Boston. April 20, 2015. (From left) Kenya’s Caroline Rotich, and Ethiopia’s Mare Diaba and Buzunush Deba, run across the 25.2-mile mark in Kenmore Square during the 119th Boston Marathon. Rotich won the women's elite division and Diaba finished second. (Photo by: Jun Tsuboike/BU News Service)

Boston. April 19, 2015. Hundreds of people, including runners, their families and Boston residents waited in line to attend the annual Boston Marathon Pre-Race Dinner on Sunday evening, the night before the Marathon Monday. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 19, 2015. Hundreds of people waited in line around blocks outside the Boston City Hall Plaza to attend the annual Boston Marathon Pre-Race Dinner on Sunday evening, the night before the Marathon Monday. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. A group of the elite women's category run past the 13-mile mark at the 2015 Boston marathon. (Photo by: Dingfang Zhou/BU News Service)

Boston. April 19, 2015. Ohein Cheeol, right, a runner from South Korea participating in the marathon, gets his dinner at the annual Boston Marathon Pre-Race Dinner on Sunday evening, the night before the Marathon Monday. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Ethiopia’s Yemane Adhane Tsegay runs through Kenmore Square during the 119th Boston Marathon. Tsegay placed second in the Men’s Elite race. (Photo by: Jun Tsuboike/BU News Service)

Boston. April 19, 2015. The annual Boston Marathon Pre-Race Dinner on Sunday evening drew in thousands of attendees from all pockets of the world. The dinner, hosted by Boston Athletic Association, was made possible in part due to the work of more than 500 volunteers. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Chilling winds and constant rain wasn't enough to deter this group of runners from finishing the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 15, 2015. A woman looks at the countdown clock of the 2015 Boston Marathon inside a shop on Boylston Street on One Boston Day. (Photo by: Dingfang Zhou/BU News Service)

Boston. April 20, 2015. Boston resident Sarah Norcott receives her medal after completing the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 19, 2015. Wisconsin resident Kamaljit Paul, one of the runners in the Boston Marathon, grabs his dinner at the annual pre-marathon dinner on Saturday night. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 18, 2015. At the three mile mark, the second wave of runners push through the final leg of the BAA 5k. (Photo by: Gina Kim/BU News Service)

April 19, 2015. Families and individuals showed up in huge numbers to attend the annual Boston Marathon Pre-Race Dinner on Sunday evening. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 19, 2015. After people run out of seats, they find comfort in stairs inside the city hall plaza as thousands attended the annual Boston Marathon Pre-Race Dinner on Sunday. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 19, 2015. Members of the Team Inside Track from Ventura, CA, including runners and their supporters, enjoy the annual pre-dinner at the Boston City Hall Plaza on Sunday. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 19, 2015. More than 500 volunteers were working at the annual Boston Marathon Pre-Race Dinner on Sunday where thousands of attendees from all pockets of the world came to enjoy their dinner the day before the Marathon Monday. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 19, 2015. Ron Guetter from Willmar, Minn. enjoys his dinner with his wife, Mary, and his daughter, Dana, at the annual Boston Marathon Pre-Race Dinner on Sunday. The mother-daughter came all the way to Boston to cheer on Ron, who will be running in Boston Marathon tomorrow. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 18, 2015. A proud mother who participated in the BAA 5k as her family cheered her on, poses for a photo with her two children after finishing the race. (Photo by: Gina Kim/BU News Service)

Boston. April 18, 2015. The true picture of life transitions - while the two men on either side of David don’t have their name and registration tags, they help their friend cross that finish line together to the end. (Photo by: Gina Kim/BU News Service)

Boston. April 20, 2015. First time runner Elizabeth Sail, 32, and Erica Gennaro, right, 30-year-old from Somerville running in her second marathon, take the T on their way to board the bus to the starting line at Hopkinton on Monday morning. (Photo by: Pankaj Khadka)

Boston. April 18, 2015. Thousands make their way through the beginning of the racecourse in a steady stream of different colors, backgrounds, Boston Strong shirts, and Martin Richard 8 jerseys, all with a personal reason - some running for personal accomplishment, some for different foundations, and all remembering those that tragically lost their lives two years ago. Four young boys stand proud, two of whom are wearing the Martin Richard 8 jerseys. (Photo by: Gina Kim/BU News Service)

Boston. April 20, 2015. Volunteers take shelter from rain as they pack lunches for the marathon runners early Monday morning near the finish line on Boylston Street. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 18, 2015. As over 10,000 registered 5k participants quickly make their way towards the starting line, a man dons his Martin Richard 8 shirt, paying tribute to the eight-year-old young boy who tragically died in the 2013 marathon bombing. (Photo by: Gina Kim/ BU News Service)

Boston. April 20, 2015. Marcel Hug of Switzerland with the crown after he wins the men's wheelchair division of the 2015 Boston Marathon Monday . (Photo by: Pankaj Khadka/BU News Service)

Boston. Apr.18, 2015. Mathew Dimatteo, a 25-year-old runner from Boston, displays his marathon running number at Hynes Convention Center on Saturday. Dimatteo, a first-time runner, is running for a charity group for bladder cancer research. "I can't think of a better event that does bond people together than Boston Marathon," said Dimatteo. (Photo by: Haiyun Jiang/BU News Service)

Boston. April 20, 2015. Winner of the women's division of the 2015 Boston Marathon, Carolina Rotich from Kenya, at the finish line. (Photo by: Pankaj Khadka/BU News Service)

Boston. Apr.18, 2015. 2015 Boston Marathon runners picked up numbers and apparels at the Hynes Convention Center on the weekend before Marathon Monday. (Photo by: Haiyun Jiang/BU News Service)

Boston. April 20, 2015. Chilling winds and constant rain wasn't enough to deter this group of runners from finishing the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. Apr.18, 2015. Yellow tulips bearing "Boston Strong" stickers, placed in memory of 2013 Boston Marathon Bombing victims and survivors, can be seen everywhere on the Bolyston Street. (Photo by: Haiyun Jiang/BU News Service)

Boston. Apr.18, 2015. A volunteer of 20105 Boston Marathon was assisting a runner with number picking-up at Hynes Convention Center. (photo by: Haiyun Jiang/BU News Service)

Boston. Apr.18, 2015. Michael Melamed, a long distance runner with muscular dystrophy from Venezula, picks up his number for 2015 Boston Marathon at Hynes Convention Center on Saturday. Melamed, who has prevously run in marathons such as New York, Berlin and Chicago is coming to Boston, which is his last stop. (Photo by: Haiyun Jiang/BU News Service)

Boston. Apr.18, 2015. Ed Talbot, who has been participating as a runner in the Boston Marathon for 26 years, is serving as volunteer this year. "It is an opportunity to be associated with this very special event," said Talbot. (Photo by: Haiyun Jiang/BU News Service)

Boston. Apr.15, 2015. Boston Police started blocking the traffic on Boylston Street on Wednesday morning, the One Boston Day, before the raising of the honorary banner in memory of 2013 Boston Marathon bombing victims. (photo by: Haiyun Jiang/BU News Service)

Boston. April 15, 2015. Mayor Marty Walsh walks with members of the Richard family during a banner unveiling to kick off the One Boston Day, an annual tradition that celebrates the resiliency, generosity, and strength of Bostonians. The banner was unveiled at 755 Boylston Street where Martin Richard, 8, was killed in the second explosion at the 2013 Boston Marathon bombing. (Photo by: Dingfang Zhou/BU News Service)

Boston. April 15, 2015. Members of the Richard family unveil an honorary banner in remembrance of the bombing victims to kick off the One Boston Day, an annual tradition that celebrates the resiliency, generosity, and strength of Bostonians. The banner was unveiled at 755 Boylston Street where Martin Richard, 8, was killed in the second explosion at the 2013 Boston Marathon bombing. (Photo by: Dingfang Zhou/BU News Service)

Boston. Apr.15, 2015. Mayor Walsh unveiled honorary banner on lightposts on Boylston Street with members of the family of Martin Richard, who was killed in the 2013 Boston Marathon bombing. (Photo by: Haiyun Jiang/BU News Service)

Boston. Apr.15, 2015. Media gathered on the Boylston Street, across from where Mayor Walsh unveiled honorary banners in remembrance of the Boston Marathon Bombing victims. (Photo by: Haiyun Jiang/BU News Service)

Boston. Apr.15, 2015. Jeff Bauman, who lost both his legs during the bombing, put his arm around Carlos Arredondo (in blue shirt), who had rushed to his aid after the blast. (Photo by: Haiyun Jiang/BU News Service)

Boston. April 15, 2015. Jeff Bauman, who lost his legs in 2013 Boston Marathon Bombing, walks towards the Boston Pulic library on One Boston Day, an annual tradition to celebrate the resiliency, generosity, and strength of Bostonians. (Photo by: Dingfang Zhou/BU News Service)

Boston. April 15, 2015. A woman looks at the countdown clock of the 2015 Boston Marathon inside a shop on Boylston Street on One Boston Day. (Photo by: Dingfang Zhou/BU News Service)

Boston. April 15, 2015. A bouquet of flowers was placed near the finish line of the Boston Marathon in memory of bombing victims. (Photo by: Haiyun Jiang/ BU News Serivice)

Boston. Mayor Martin Walsh joined City Hall staff to observe "A Moment of Silence" event in honor of Boston Marathon Bombing victims. (Photo by: Haiyun Jiang/BU News Service)

Boston. April 20, 2015. Runners board a shuttle bus at Boston Common as they head to the starting line in Hopkinton for the 119th Boston Marathon. ( Jun Tsuboike/BU News Service)

Boston. April 20, 2015. Runners arrive at the Boston Common to board the shuttle bus to the starting area in Hopkinton for the 119th Boston Marathon. (Photo by: Jun Tsuboike/BUNS)

Boston. April 20, 2015. Runners board onto a shuttle bus at the Boston Common to the starting area in Hopkinton for the 119th Boston Marathon. (Photo by: Jun Tsuboike/BUNS)

Boston. April 20, 2015. Runners board onto a shuttle bus at the Boston Common to the starting area in Hopkinton for the 119th Boston Marathon. (Photo by: Jun Tsuboike/BUNS)

Boston. April 20, 2015. Security personnel check the number tags and bags of the runners as they head towards the buses to go to the starting line before the start of the marathon. (Photo by: Pankaj Khadka)

Boston. April 20, 2015. The Penteke family from Minnesota came all the way down to Boston to cheer on thier family member Brittany who is competing in the Boston Marathon for the second time. (Photo by: Pankaj Khadka)

Boston. April 20, 2015. Runners board onto a shuttle bus at the Boston Common to the starting area in Hopkinton for the 119th Boston Marathon. (Photo by: Jun Tsuboike/BUNS)

Boston. April 20, 2015. Hundreds of people gather near the finish line and take photos of the giant screen before the start of the 2015 Boston Marathon race. (Photo by: Pankaj Khadka)

Boston. April 20, 2015. Volunteers at the 2015 Boston Marathon Monday hold the medals near the finish line on Boylston Street on Monday morning. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Marcel Hug of Switzerland right before he crossed the finish line to win the men's wheelchair division of the 2015 Boston Marathon Monday . (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Marcel Hug of Switzerland with the crown after he wins the men's wheelchair division of the 2015 Boston Marathon Monday. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Mare Dibaba from Ethiopia, orange, leads the women's Boston Marathon 2015 moments before the eventual winner Carolina Rotitch from Kenya takes over her with 500 feet remaining between them and the finish line. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Winner of the women's division of the 2015 Boston Marathon, Carolina Rotich from Kenya, green, pulls away from Mare Dibaba of Ethiopia, orange, in the last 500 feet. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Winner of the women's division of the 2015 Boston Marathon, Carolina Rotich from Kenya, goes to the ground in celebration. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Winner of the women's division of the 2015 Boston Marathon, Carolina Rotich from Kenya, goes to the ground in celebration. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Ethiopian runner Lelisa Desisa, the winner of the men's elite division of the 2015 Boston Marathon, moments before he crosses the finish line. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Lelisa Desisa, the winner of the men's elite division of the 2015 Boston Marathon, moments before he crosses the finish line. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Lelisa Desisa from Ethiopia, the winner of the men's elite division of the 2015 Boston Marathon, takes long strides with only a few yards remaining to cross the finish line. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. As he steps on the finish line, Lelisa Desisa, the winner of the men's elite division of the 2015 Boston Marathon, raises his hands in the air in celebration. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Lelisa Desisa crosses the finish line to win the men's elite division of the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Lelisa Desisa with the winner's trophy after winning the men's elite division of the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Photographers gather in front of Ethiopian Lelisa Desisa, the winner's trophy after winning the men's elite division of the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Marcel E. Hug was one of the first to pass the 23 miles mark near Coolidge Corner. He eventually finished the marathon in one hour 29 minutes and 53 seconds to win the 2015 Boston Marathon men's wheelchair category. He has previously won the 2011 and 2012 Berlin Marathon, 2013 New York City Marathon and the 2014 London Marathon. (Photo by: Simeng Dai/BU News Service).

Boston. April 20. 2015. 70 participants joined the push-rim wheelchairs marathon. An athlete passed by Coolidge corner. (Photo by: Simeng Dai/BU News Service)

Boston. April 20, 2015. A crowd on Boylston Street gathers near the 2015 Boston Marathon Finish Line to watch the runners of Boston Marathon, the longest continuing marathon in the world. (Photo by Genevieve Scarano/BU News Service)

Boston. April 20, 2015. National flags from various countries are present at the 2015 Boston Marathon Finish Line. (Photo by Genevieve Scarano/BU News Service)

Boston. April 20, 2015. Emerson College Graduate Students Lydia Lefevre and Jackie Dimura hold up a Boston Strong sign at the 2015 Boston Marathon Finish Line on Boylston Street. (Photo by Genevieve Scarano/BU News Service)

Boston. April 20, 2015. 2015 Boston Marathon runners brave cold winds and rain on Boylston Street as they sprint towards the finish line. (Photo by: Genevieve Scarano/BU News Service)

Boston. April 20, 2015. A group of runners approach the finish line of the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Boylston Street reflects the shadows of the runners as they approach the finish line of the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Rain and cold winds resulted in almost empty bleachers next to the finish line as runners stride towards it during the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Security personnel monitor Kenmore Square from the rooftop of Hotel Buckminster. (Photo by: Jun Tsuboike/BU News Service)

Boston. April 20, 2015. Runners pass through Kenmore Square during the 119th Boston Marathon (Photo by: Jun Tsuboike/BUNS)

Boston. April 20, 2015. Ethiopia’s Lelisa Desisa runs through Kenmore Square during the 119th Boston Marathon. Desisa placed first in the Men’s Elite race. (Photo by: Jun Tsuboike/BU News Service)

Boston. April 20, 2015. Spectators watch runners through the glass canopy in Kenmore Square during the 119th Boston Marathon. (Photo by: Jun Tsuboike/BUNS)

Boston. April 20, 2015. Spectators at Boylston Street cheer on the 2015 Boston Marathon runners. (Photo by Sharanya Pillai/BU News Service)

Boston. April 20, 2015. A small memorial, dedicated to the four victims of the 2013 Boston Marathon bombings, on the sidewalk of 939 Boylston Street. (Photo by Sharanya Pillai/ BU News Service)

Boston. April 20, 2015. Rebecca Smith, 42, from Richland, Miss. kisses her 2015 Boston Marathon medal as she tears up in joy. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. All streets around Boston Common and near the finish line were filled with thousands of runners and viewers during the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Michele Conde from Dracut, Mass. hugs her brother, Anthony Pappalardo, also a Dracut resident, after he completes the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Amy Griffith, 57, from Atlanta poses with the medal after completing the 2015 Boston Marathon. This was Griffith's third time in Boston Marathon, and at three hours and 57 minutes, this was her best time yet. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. A woman runner takes a moment to reflect on her achievement after completing the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Members of the medical assistance at Boston Marathon help an elderly runner catch his breath after he crossed the finish line. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. A runner finds warmth under the official blanket of the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Runners brave the bone-chilling winds and ice-cold rain while holding on to their blankets after completing the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. 39-year-old Monica Shields, center, from Hope, Maine, celebrates with her friends after completing the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. 31-year-old Shannon Hammerschmidt from Lincoln, Nebraska finds comfort, and warmth, in her boyfriend Ryan Christensen's arms after she completed the 2015 Boston Marathon. This was Hammerschmidt's third time in the historic Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Emotions were running high among the 2015 Boston Marathon runners after they completed the 26-mile long journey past the finish line. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Two women runners congratulate each other with tears of joy after completing the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Family members of one of the 2015 Boston Marathon runner wait near the finish line. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Boston resident Andreia Muhlbeier, 43, expresses her emotions through tears after completing the 2015 Boston Marathon. Muhlbeier had previously run in the tragic 2013 marathon which, she said, she hadn't been able to finish. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Boston resident Andreia Muhlbeier, 43, can barely hold her emotions back as walks after completing the 2015 Boston Marathon. Muhlbeier had previously run in the tragic 2013 marathon which, she said, she hadn't been able to finish. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Cambridge resident Rachel Pettis, 24, breaks down in tears as she hugs her mother, Patti, after completing the 2015 Boston Marathon. Pettis said the weather was somewhat challenging but noted that she was feeling awesome as she let her tears express her joy. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. For some runners, completing the marathon was just another item off their list; for some, it was a disbelief. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. For many marathon runners, completing the 26-mile stretch was an overwhleming experience. A woman moments before she broke into tears across the finish line at the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Hats off to you, sir! A man takes off his hat and poses for the camera after completing the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. A runner shrieks in joy after completing the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Some sighed in relief; others broke into tears as they stepped across the finish line at the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. A couple of runners take a selfie post-completion of the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. A runner takes a knee and says a prayer just before stepping on the finish line at the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. A runner looks towards the sky as she steps across the 2015 Boston Marathon finish line. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. A runner donned in a Spartan costume raises his sword in celebration after completing the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. A runner jumps his way into the finish line of the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. A runner punches the air emphatically in celebration after completing the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. A runner breathes in the air across the finish line of the 2015 Boston Marathon after completing the course. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. A 26-mile run is an achievement in itself, and many runners gave their all to cross the celebrated blue and yellow finish line at the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Some celebrated in tears; others rejoiced with waving arms after completing of the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Emergency personnel wait for assistance as three runners lock arms-in-chain to carry a fourth runner across the finish line as they all complete the 2015 Boston Marathon together. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. A runner raises his hands in celebration as he steps on the finish line of the 2015 Boston Marathon. (Photo by: Pankaj Khadka/BU News Service)

Boston. April 20, 2015. Steffany Ryan, Julie Hamrick and Hayworth Szymborsky from Charlotte, North Carolina, hold signs and cheer for Ryan's sister Joan Dodson, at 2015 Boston Marathon. "She wants to have a good run and to complete and cross the finish line," said Ryan. "The marathon not only bonds people in the city, but also the running community in the world, together." (Photo by: Haiyun Jiang/BU News Service)

Boston. April 20, 2015. Kathy Drill, left, mother of Josh Whitcraft, a runner in the 2015 Boston Marathon, and his girlfriend Christiana Bromberg, wait near the finish line. (Photo by: Xuedong Wang/ BU News Service)

Boston. April 20, 2015. Two military veteran runners approach the finish line of 2015 Boston Marathon. (Photo by: Haiyun Jiang/BU News Service)

Boston. April 20, 2015. Crowds gather below the giant monitor screen near the 2015 Boston Marathon finish line on Boylston Street and watch live coverage of the marathon. (Photo by: Haiyun Jiang/BU News Service)

Boston. April 20, 2015. Matthew Clarke, who has run marathons in New York, Berlin and London, finished his first Boston Marathon in 2 hours and 11 minutes. Originally from the United Kingdom, Clarke described the audience of Boston as brilliant. "They cheered you up despite the cold temperature. It's been a good day," said Clarke. (Photo by: Haiyun Jiang/BU News Service)

Boston. April 20, 2015. Michael Palizzolo, a security personnel during patrol on Boylston Street at the 2015 Boston Marathon. "I'm patrolling to make sure everything is safe," said Palizzolo. (Photo by: Haiyun Jiang/BU News Service)

Boston. April 20, 2015. One of the runners at the 2015 Boston Marathon. (Photo by: Xuedong Wang/ BU News Service)

Boston. April 20, 2015. Wisconsin resident Allen Bausch approaches his daughter, Carly, who waited in the wind and rain at Wellesley College for more two hours hug to her father and cheer for him. (Photo by: Dingfang Zhou/BU News Service)

Boston. April 20, 2015. Carly Bausch waits near Wellesley College to cheer for her father Allen Bausch, a second time Boston Marathon runner from Wisconsin.(Photo by: Dingfang Zhou/BU News Service)

Boston. April 20, 2015. Marathon runners interact with the crowd that was clapping, cheering, and even screaming near Wellesley College, which is known as the “Screaming Tunnel”, a popular spot to watch the Boston marathon. (Photo by: Dingfang Zhou/BU News Service)

Boston. April 20, 2015. A runner in the wheel chair category at the 2015 Boston Marathon. (Photo by: Xuedong Wang/ BU News Service)

Boston. April 20, 2015. Local favorite Shalane Flanagan, resident of Marblehead, finished ninth in the 2015 Boston Marathon. She finished seventh in the last year's edition despite leading for more than half of the marathon and was a strong contender this year. (Photo by: Gina Kim/BU News Service)