One man, Ron Brassard, had blood pouring out of a leg. He screamed in pain and yelled, "I'm not going anywhere without my daughter."
He repeated it over and over and over.
More 'Apollo 13' than 'ER'
"There was an explosion at the finish line."
That was the message relayed to Dr. Horacio Hojman, the associate director of trauma and the surgical director of the intensive care unit at Tufts Medical Center.
He and his staff instantly activated the hospital's emergency response plan. Four trauma teams, each consisting of four medical staff -- an ER attendant, two residents and an intern -- scrubbed in. They quickly cleaned the emergency room, wiping everything down, mopping the linoleum floors and preparing the rooms. Patients already there were moved to other parts of the hospital.
In less than 10 minutes they were ready.
Born in Argentina, Hojman had treated patients of mass shootings and explosions in his homeland. He's lived in the United States for more than 20 years and has always preached to his staff about the need to be prepared for worst-case scenarios.
Everyone on his emergency team has gone through what he calls "the simulator" at Tufts medical school to prepare for a moment like this. It's a facility designed just like an ER to teach doctors to keep calm under pressure.
The idea, he said, is to make the training "so difficult that, by comparison, this seems to be easy."
"When we think we have these things nailed down, we train a little bit more."
Soon, ambulances were radioing in: About 20 patients were headed their way, including at least four in danger of losing limbs.
The Hollywood version of chaotic emergency rooms, Hojman said, gets it all wrong.
"This is absolutely not the way it happens in a real trauma situation."
He tells his residents to think of the movie "Apollo 13" and how calm NASA engineers remained when they were told, "Houston, we have a problem."
The emergency room, he said, is more choreographed than synchronized swimming.
A brief silence filled the ER, and then the ambulances arrived.
Staff set up four trauma bays. One doctor was in charge of assigning patients to each bay to make sure patients didn't back up.
Each patient was marked by ambulance EMTs with red, yellow or green -- red for the most critical. Patients were stripped of clothes, examined and evaluated quickly. The four critical patients were sent to emergency surgery on a separate floor to try to save their legs.
Later, Hojman would be called into surgery for a fifth patient, the weight of saving the patient's limb -- and life -- paramount.
"In every surgeon's mind," he said, "you think, 'I need to do everything possible to save this limb.' I think that we as surgeons refuse to accept failure. ... But the injuries were very, very serious."
Another problem soon arrived -- one the simulator hadn't prepared them for. About 30 minutes after the first patients arrived, a suspicious package was found in the emergency room. An evacuation was ordered, and police swept the facility.
Patients were moved outside to the street.
Hojman and a colleague went from room to room to make sure no patients were left behind. He stopped to tell two officers near the room with the package that they should leave, too.
"If there's an explosion, there's no way you or your buddy will be able to survive," he told them.
Both gave the doctor stern looks, like he was crazy. "When I had the sense that I was probably going to get arrested," he said, "I decided to leave."
Once outside, he looked at the glass windows of the hospital's façade. He knew that in the twin embassy bombings in Kenya and Tanzania in 1998, the worst wounds came from shards of glass.
Looking up at the building he loved, Hojman now worried that if a bomb exploded, the patients lined up outside might be wounded again -- this time by flying glass.
He ordered the patients moved to the hospital lobby. All the while, the trauma teams worked to keep everyone alive, monitoring their vital signs and making sure they remained hooked up to IVs.
The hospital went into lockdown moments after the patients filled the lobby. "That created another problem," he said. One resident physician got locked out.
"Again, it's all training. It's all focus," he said. "At the end of the day, you have to remember you're treating human beings and that's the reason we're doing it. We're not doing it for anything else."
Learning his patients' fate
Ron Brassard, 51, was missing a chunk of his left leg when he arrived at Tufts. Runners had sprinted to his side, taking off their shirts and wrapping his leg, before he reached Segatore in the medical tent, screaming for his daughter. From there, EMTs rushed him to Tufts.
Hojman's trauma team worked to save him and his limb. He was among the four patients taken to emergency surgery.
The next day, from his bedside, he recalled watching the marathon, having a good time with everyone "laughing and smiling, and then all of a sudden. ..." The first bomb, he said, went off about 10 feet away.
"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."