Story highlights Segatore: "No one expects to work at the (marathon) and end up at a terrorist attack"

One young woman's abdomen was torn open; she didn't make it

Asaiante's experience in the Iraq War told him the blast was an IED

Of all the Boston Marathons he's worked, and he's done a half-dozen of them, Stephen Segatore figured this one would be pretty easy.

The weather was cool, so the runners probably wouldn't be at much risk for heat stroke or dehydration. Maybe he'd help people with muscle cramps or twisted ankles, but not much more than that.

Segatore, a nurse for 18 years, started his day Monday with the elite athletes in Medical Tent B toward the start of the race. Once those runners were well on their way, he transferred to Tent A at the finish line. He was talking to a group of doctors and nurses when they heard the first explosion.

Instantly, a team meant to tend to the achy and exhausted became a trauma team. The first step: those who didn't have experience with trauma stepped aside. Those with experience dashed out in the direction of the noise.

Segatore, who works in the intensive care unit at nearby Tufts Medical Center, had experience.

"I ran out and saw people who were missing legs and part of their face and part of their abdomen," he said Monday evening. "My training prepared me for what to do, but nothing can ever really prepare you for what you see."

Photos: Deadly attack at Boston Marathon Photos: Deadly attack at Boston Marathon An injured man is loaded into an ambulance after two bombs went off near the finish line of the Boston Marathon on April 15, 2013. Three people were killed and at least 264 were injured. Hide Caption 1 of 55 Photos: Deadly attack at Boston Marathon A man comforts a victim on the sidewalk at the scene of the first explosion. Hide Caption 2 of 55 Photos: Deadly attack at Boston Marathon The second explosion goes off near the finish line. Hide Caption 3 of 55 Photos: Deadly attack at Boston Marathon The first explosion knocked down 78-year-old runner Bill Iffrig at the finish line. He got up a few minutes later and finished the race. Hide Caption 4 of 55 Photos: Deadly attack at Boston Marathon A runner embraces another woman on the marathon route near Kenmore Square. Hide Caption 5 of 55 Photos: Deadly attack at Boston Marathon Former New England Patriots offensive lineman Joe Andruzzi carries a woman from the scene. Hide Caption 6 of 55 Photos: Deadly attack at Boston Marathon A victim of the first explosion is helped on the sidewalk of Boylston Street. Hide Caption 7 of 55 Photos: Deadly attack at Boston Marathon An injured person is taken away from the scene in a wheelchair. Hide Caption 8 of 55 Photos: Deadly attack at Boston Marathon A woman kneels and prays at near the finish line. Hide Caption 9 of 55 Photos: Deadly attack at Boston Marathon People run down Exeter Street after the blasts. Hide Caption 10 of 55 Photos: Deadly attack at Boston Marathon The explosions occurred around 2:45 p.m., about an hour after the first of the race's nearly 27,000 runners had crossed the finish line. Hide Caption 11 of 55 Photos: Deadly attack at Boston Marathon Victims lie on the ground at the scene of the first explosion. Hide Caption 12 of 55 Photos: Deadly attack at Boston Marathon A couple runs from the scene pushing a stroller. Hide Caption 13 of 55 Photos: Deadly attack at Boston Marathon A runner reacts near Kenmore Square after the explosions. Hide Caption 14 of 55 Photos: Deadly attack at Boston Marathon A man's blood-stained feet hang outside an ambulance. Hide Caption 15 of 55 Photos: Deadly attack at Boston Marathon A bystander who was injured in the first explosion is wheeled across the finish line while receiving medical attention from rescue workers. Hide Caption 16 of 55 Photos: Deadly attack at Boston Marathon Carlos Arredondo was at the race handing out American flags to spectators. After the blasts, he helped emergency responders and is credited with helping a man survive serious leg wounds. Hide Caption 17 of 55 Photos: Deadly attack at Boston Marathon The second explosion goes off near the finish line. Hide Caption 18 of 55 Photos: Deadly attack at Boston Marathon Police look at blown-out windows. The bombs shook buildings, witnesses said, sending people to seek shelter under tables. Hide Caption 19 of 55 Photos: Deadly attack at Boston Marathon Unclaimed runners' bags fill an area near the marathon finish. Hide Caption 20 of 55 Photos: Deadly attack at Boston Marathon Women desperate to hear from loved ones are unable to get close to the site of the attack. Hide Caption 21 of 55 Photos: Deadly attack at Boston Marathon Police and runners stand near Kenmore Square after the attack. Hide Caption 22 of 55 Photos: Deadly attack at Boston Marathon Runners gather near Kenmore Square after the explosions. Hide Caption 23 of 55 Photos: Deadly attack at Boston Marathon An EMT worker is transferred to an ambulance outside a medical tent in Copley Square. Hide Caption 24 of 55 Photos: Deadly attack at Boston Marathon A SWAT team arrives on the scene. Hide Caption 25 of 55 Photos: Deadly attack at Boston Marathon A runner sits near Kenmore Square after the attack. Hide Caption 26 of 55 Photos: Deadly attack at Boston Marathon Runners who had not yet finished the race are stopped after the explosions. Hide Caption 27 of 55 Photos: Deadly attack at Boston Marathon Victims are helped at the scene of the first explosion. Hide Caption 28 of 55 Photos: Deadly attack at Boston Marathon A man in tears is helped at the scene on Boylston Street. Hide Caption 29 of 55 Photos: Deadly attack at Boston Marathon Passersby put pressure on a victim's leg to try to stop the bleeding. Hide Caption 30 of 55 Photos: Deadly attack at Boston Marathon Massachusetts State Police guard an area near Kenmore Square. Hide Caption 31 of 55 Photos: Deadly attack at Boston Marathon Bystanders embrace near the finish line. Hide Caption 32 of 55 Photos: Deadly attack at Boston Marathon Police officers gather on Newbury Street. Hide Caption 33 of 55 Photos: Deadly attack at Boston Marathon Women and children are escorted away from the scene. Hide Caption 34 of 55 Photos: Deadly attack at Boston Marathon Bomb squad officials check a possible suspicious device near the scene of the blasts. Hide Caption 35 of 55 Photos: Deadly attack at Boston Marathon A woman is comforted after the blasts. Hide Caption 36 of 55 Photos: Deadly attack at Boston Marathon Two injured women are taken away on stretchers. Hide Caption 37 of 55 Photos: Deadly attack at Boston Marathon An injured woman is loaded into an ambulance. Hide Caption 38 of 55 Photos: Deadly attack at Boston Marathon First responders load injured people into an ambulance. Hide Caption 39 of 55 Photos: Deadly attack at Boston Marathon An injured man is prepared to be moved from a stretcher to an ambulance. Hide Caption 40 of 55 Photos: Deadly attack at Boston Marathon An injured woman is placed on a stretcher. Hide Caption 41 of 55 Photos: Deadly attack at Boston Marathon A runner is comforted following the attack. Hide Caption 42 of 55 Photos: Deadly attack at Boston Marathon The Cambridge Police Department's bomb squad investigates unattended personal items left behind after the explosions. Hide Caption 43 of 55 Photos: Deadly attack at Boston Marathon Bystanders check their mobile devices for news of the explosions. Hide Caption 44 of 55 Photos: Deadly attack at Boston Marathon A member of the bomb squad investigates a suspicious item on the road near Kenmore Square. Hide Caption 45 of 55 Photos: Deadly attack at Boston Marathon A runner in a wheelchair is taken from a triage tent after the explosions went off. Hide Caption 46 of 55 Photos: Deadly attack at Boston Marathon People comfort each near the site of the blasts. Hide Caption 47 of 55 Photos: Deadly attack at Boston Marathon Racers and race officials stand by after the explosions. Hide Caption 48 of 55 Photos: Deadly attack at Boston Marathon Emergency personnel respond to the scene. Hide Caption 49 of 55 Photos: Deadly attack at Boston Marathon Police and emergency crews tend to victims. Hide Caption 50 of 55 Photos: Deadly attack at Boston Marathon An injured woman is carried away on a stretcher. Hide Caption 51 of 55 Photos: Deadly attack at Boston Marathon A man lies on the ground after the incident. Hide Caption 52 of 55 Photos: Deadly attack at Boston Marathon Officials watch as the first explosion goes off on Boylston Street. Hide Caption 53 of 55 Photos: Deadly attack at Boston Marathon Spectators leave the bleachers after the explosions. Hide Caption 54 of 55 Photos: Deadly attack at Boston Marathon Police inspect one of the blast sites. Hide Caption 55 of 55

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Segatore was one of a team of dozens of doctors and nurses who volunteered at Monday's Boston Marathon. They worked quickly to stop bleeding and start IVs so patients could get into ambulances and to hospital emergency rooms. They treated dozens of patients without proper supplies for severe trauma, such as dressings and pain medications.

"No one expects to work at the Boston Marathon and end up at a terrorist attack," he said.

One of his first patients was a young woman, he thinks maybe 20 or 22 years old, whose abdomen was torn open. Her left leg was broken and facing the wrong way and she wasn't breathing. He and his colleagues did CPR on her and kept checking for a pulse, but there was none. They stopped when they realized it was futile.

She became the first patient in their makeshift morgue.

Segatore and others checked her pockets for a wallet, an ID, a cell phone, anything that would help them find her parents' names. There was nothing.

"I still don't know who she was," he said. "She had blonde hair, blue eyes, the all-American girl. She was probably a student somewhere in Boston."

"I've seen people die all over the world, but I've never been this upset or angry in my career," Segatore said. "This is the Boston Marathon. People come from all over the world and all of a sudden that world exploded on them."

Working alongside Segatore in Tent A was Jim Asaiante, a nurse in the emergency room at the UMass Memorial Medical Center in Worcester, Massachusetts. Asaiante didn't run out after the explosion. He has plenty of experience in trauma, but as a veteran of the Iraq War, he's also had plenty of experience with explosions.

"I heard the first IED (improvised explosive device), and I know there's never one. The bad guys always set up two or three," said Asaiante, an Army captain who did an 18-month tour in Iraq in 2006 and 2007.

Another victim was brought into the tent, a man with his calves and feet blown off and blood pumping out of his knees. Asaiante put a tourniquet on him, started an IV, and in 15 minutes the man, who was screaming in pain, was in an ambulance.

After the second explosion, Asaiante ran out of the tent.

"There was lots of bleeding, shrapnel, glass. It was mayhem," he said. "The injuries were very similar to Iraq."

Despite the chaos, he said the work of the doctors, nurses and EMTs was "impeccable."

Segatore agreed.

"The most amazing thing was how everyone worked in tandem. They didn't even have to speak a word between each other," he said. "In 20 years of nursing, this was the most amazing two hours of nursing in my life."