When Natalie Stavas and her father finally reached mile 26, drained but determined to finish, they heard the boom of the explosions and watched as police began erecting barricades to block runners from continuing to the finish line.
Father and daughter knew something was terribly wrong; and despite their fatigue, they knew they had to help.
So Stavas, 32, a pediatric resident who now works in Boston and was running with a broken foot, leaped over a barricade. Police screamed for her to stop, she says, but she kept running toward Boylston Street. "I yelled at one officer, saying, 'I'm a pediatric doctor. You have to let me through.' "
As depleted as she was after running all but the final two-tenths of the Marathon, she sprinted, ignoring the police who couldn't keep up with her. "I was running like a bat out of hell," she said. "I wasn't aware of my fatigue."
She was running toward the explosion, and police kept trying to stop her.
When she made it to the scene of the second explosion beside Atlantic Fish Co., she found a young woman bleeding profusely from a blown-open thigh. She immediately began pumping the unconscious woman's chest and directing others to provide oxygen through an ambu bag someone had supplied. She showed others how to apply pressure to the woman's legs.
When paramedics took the woman away, Stavas ran about 30 feet down Boylston until she found another young woman lying on her back with a massive hole in her groin. "As soon as I saw the wound," she said, "I began screaming that this woman needed to be sent to a hospital."
The woman was shivering, and Stavas borrowed a jacket from someone, which she used to cover the woman's wounds. With the woman stabilized, she got up and ran toward the site of the first explosion to help a man lying on his back with a mangled foot. Someone handed her a tourniquet, and with all her strength, she applied it above his knee.
"I had to apply so much pressure that the man thought he was going to die," she said. "He was screaming."
Afterward, she treated a young man whose tibia was protruding through his skin above his ankle.
"I've never seen anything like that before - like a true, utter battle zone," she said. "I thought, how could someone do this to so many innocent people?"
Meanwhile, her father, Joe Stavas, 58, a radiologist who now works in North Carolina, was helping tend to some of the thousands of runners who were halted at Hereford Street. Many were growing cold quickly after sweating, which can be dangerous for marathon runners.
He found an elderly runner who was ashen, lacked much of a pulse, and had passed out. "She was white as a sheet," he said of the woman. "I knew it was hypothermia."
He and others bundled her in a coat, hat, and blankets from spectators, and carried her to a nearby restaurant. "We knew it would be impossible for an ambulance to get to her," he said.
Afterward, Joe Stavas found a young woman who was crying so hard she couldn't speak. Her fingers were so cold she could barely open them. "I saw goose bumps on her face, which is rare," he said.
He gave her his hat and jacket and his daughter's gloves.
Over the next hour, he helped at least a half dozen people, carrying them to nearby townhouses where residents opened their doors.
"I see this like getting through a marathon, and we're on Heartbreak Hill," Joe Stavas said.