"It was so close that you couldn't hear after the explosion," he told CNN's Anderson Cooper, his left leg wrapped and propped up. "The noise was, I think, scarier than the blast itself because it was so loud."
Immediately after the blast, an incredible pain shot through his leg, and an unbearable thought kept going through his mind: Where is my daughter?
His wife told him their daughter, Krystara, 20, was right there, he recalled later, but at the time he couldn't hear because the blast left him briefly deaf.
He didn't look at his leg "because I knew something was wrong." He just remembers that every time he took a step there was a puddle of blood the "size of a dinner plate."
It wasn't until he made it to the hospital that he got the courage to look at his wound. "It wasn't anything fun to look at."
It was also at the hospital where he found out his daughter was alive. She had shrapnel wounds from head to toe, and her mother, Karen, had two large shrapnel pieces embedded in both of her legs. They'd been taken to Boston Medical Center.
But two of their friends suffered much worse. Sydney Corcoran -- a 17-year-old high school senior who had survived being hit by a car in 2011 -- had her legs shredded in the blast; her mother, Celeste, had both legs amputated below her knee.
Segatore, who'd heard Brassard screaming for his daughter in the medical tent, learned from the news that he and his family had survived. He was glad to know Brassard's leg was saved, too, especially at the hospital where he works.
But there's one image he can't shake -- and that's of the woman who couldn't be saved. "Her face, because I was right there over her," he said, "it's in my memory."
He had searched for identification but found nothing on her body. He's since learned that she was Krystle Campbell, one of three people killed in the attack. He recognized her photo in the news instantly because of "her big blue eyes and blue eye shadow." He wants her family to know that she didn't die alone.
Asaiante, the Iraqi war veteran, wished the terror had never struck his city, but he was proud to be able respond. "All of us found ourselves in extraordinary circumstances, and we just did what we had to do," he said.
Just like pushing through the pain of conquering the infamous Heartbreak Hill at mile 20, Bostonians are resilient and will work together to recover from the tragedy. "Push on through it," he said, "don't forget it and make a positive."
More than 170 people were treated for their wounds at hospitals. Thirteen have had limbs amputated. Authorities have said the death toll likely would have been much higher if it weren't for the actions of so many first responders.
Back near the finish line, at the foot of police barricades, a makeshift shrine sits at the corner of Boylston and Berkeley streets. Mourners come to pay their respects and leave flowers and other mementoes.
One sign carries the famous quote of childhood TV show icon Mr. Rogers: "When I was a boy and I would see scary things in the news, my mother would say to me, 'Look for the helpers. You will always find people who are helping.' "
Last Monday, the helpers sprang forward.