Transcript for Boston Marathon Runners Return to Honor Last Year's Bombing Victims
This is a special room. I'm -- Cutler and New York. -- patriots day in Massachusetts and this very special -- eighteenth running of the Boston Marathon is under way. 26 point two miles from Hopkinton to back bay and of course that hallowed finish line on Boylston street. In the shadow of the Boston Public Library -- live look. At the marathon we -- you have two winners thirty year old med Kozlowski is the first American citizen to win a race since 1983. For the women it is -- Jeff to for the second straight -- join a title she said she could not celebrate. After last year's bombing with more on the bittersweet day in Beantown here's ABC's Mark Bradley. -- -- -- -- Before the race a moment of silence to remember the victims of last year's attack. And then Boston's triumph over terror 36000. Runners setting out for the 26 point two mile -- Because of loss of life. Sean Scalia Lesley -- pixel camera in my religion this marathon is about as much supporting those families lost loved -- Back this year some of the survivors from that fateful day they're running with six Massachusetts general nurses all of whom treated victims that's going to be very -- now. I mean it's that the emotions just -- -- last week have plagued quadrupled. Organizers -- for a million spectators this year double the usual turnout. The security is extraordinary. More than a hundred cameras along the marathon route monitored at a special underground high tech senator. Above ground up 4000 police officers 500 of them under cover. For Boston today as a celebration of the city's resilience. These two Brothers JP and -- -- each lost the leg in the attack but even after fifty surgeries between them they both say they. New outlook on life. -- -- -- -- -- -- -- -- A year ago and I'm just very happy now before I would have set as the just content but now -- happy. Austin -- it or waiting for their loved ones to finish the race so far we've not heard any reports of any security prop. To Ron Bradley -- -- -- -- -- characters here who is live in Boston at this hour Aaron you spent. Your whole morning the finish line on Boylston street what did you see there what stood out to you. Some extraordinary moments really dead at the finish line where runners were crossing the finish line to the cheers of the. Crowd and and the runners would turn and applaud right back and -- and the crowd and I -- some of the runners -- you would applaud the of the spectators that have come on the civil this is for them. -- -- said he's not running for himself this wasn't about a personal best store. Getting a better time this was all about. Thanking the citizens of Boston. Aaron I know -- there -- a number of tributes going on across the city today but one very special event inside the city's most celebrated stadium right. At Fenway Park last night they honored some of the first responders some of the volunteers they'd been having these kinds of tributes. All across the city all really all year and they want to make sure that people understand there were extraordinary moments. In some of the awful. Happenings of last year's race and in those extraordinary moments many of the runners told me again that they found. Nothing to reclaim this -- I have Brothers did not succeed in taking anything away from this race and so they didn't think that there was any reason to run in defiance because there was nothing to -- Just the very heroic actions of the first responders running toward the explosions these -- said. But was -- else and nonetheless the spectators are back out the runners are back there was an important psychological component to this race. In as much as this is a physical challenge there is a psychological challenge here -- to show the world Boston is back on the street. Boston strong in fact as well but at the same time though -- there have been some very tangible differences. In the precautions. For the race this year -- a little bit about some of the differences. -- right at the finish line you see it there are dogs sniffing around anything discarded on the sidewalk anybody carrying -- bag -- backpack larger than an average purses in for a little more scrutiny. We saw some snipers perched up on rooftops helicopters were overhead. And despite all of that the mood still seemed more festive. Then fearful and that was all true during the Easter weekend to glorious weekend here in Boston when people would come down and take pictures -- the finish line and it endured today. When some of the runners -- this was allowed -- crowd they had ever heard now along the way in pockets. It seemed to longtime race observers that maybe the crowd was a little bit thinner than it has been in years past. But you come down Boylston street to the finish line and it was boisterous and many of the runners said. That really gave them the -- needed. The winners crossed the finish line but still though long way to go for their entire merit not so what do you expect the last -- to cross the line. Notably well into the early evening I think in the security posture is going is today remembered it was 2:49 PM eastern time. When the bombs exploded on Boylston street twelve seconds apart 550 feet apart. And so that was long after the elite runners and the first wave had crossed and in fact we've spoken to a lot of those elites who said they can't even think. About celebrating their finish from last year because of what happened and this -- given them -- new chance to prove themselves and auntie to show the world what good runners they are but it's also. Given the entire city chance to -- clean this race and elevated. From what it became known as last year. -- don't have little slogan Boston strong. Certainly presents yet never more sure that they like today so tell me a little bit about the winner that 38 year old med complicity. He's the first American to win since 1983. He became a naturalized citizen. About ten years ago and he is the one of the oldest winners of the Boston Marathon he's about to turn 39 years old. And there was a great moment he crossed the finish line he put the crown on -- that he came to chat with a few of us and he said I am -- strong and I think that resonated. Are around all of Copley Square for sure but once people hear what he said. I think that's also going to resonate because so many of the runners have adopted Boston even if they have no natural connection of the city. Never more sure and never more appropriate for a winning story ABC caricature -- in Boston -- thank you for that. This has been an ABC news digital special report and you can keep up with the -- latest in real time by downloading the ABC news apps -- the sort forks was updates on ago. For now though I'm -- -- -- New York.
This transcript has been automatically generated and may not be 100% accurate.