The victims just kept coming.
In cars, in ambulances waiting four or five deep, from the walking wounded to the barely alive, they arrived in droves.
"I have no idea who I operated on," said trauma surgeon Dr. Jay Coates. The hospital where he works took in many of the wounded after Stephen Paddock opened fire from his 32nd-floor hotel suite on Sunday night, spraying bullets into a crowd of country music concertgoers below. "They were coming in so fast ... We were just trying to keep people from dying."
When Dr Coates pulled up to work at the University Medical Center of Southern Nevada on Sunday night, the surrounding streets were already cordoned off and ambulances lined the driveway, filled with the victims of the deadliest mass shooting in modern American history.
"Every bed was full," Dr Coates said. "We had people in the hallways, people outside and more people coming in. It was like a war zone."
He said the huge, horrifying wounds on his operating table told him this shooting was something different.
"It was very clear from the first patient I operated on that this was a high-powered weapon," Dr Coates said. "This wasn't a normal street weapon. This was something that did a lot of damage when it entered the body cavity."
The fusillade of bullets fired from the Mandalay Bay hotel into a crowd of 22,000 at a country music festival killed at least 59 people and sent more than 500 to area hospitals, severely straining the city's emergency response system.
University Medical Center is a level-one trauma centre, meaning it is staffed around the clock with surgeons and trauma nurses and personnel. But it is also the only level-one trauma centre in the whole state of Nevada. On Sunday night, virtually every available employee rushed back to work to be confronted with unimaginable carnage.
Toni Mullan, a clinical nursing supervisor for the trauma unit, had just got home after a 12-hour shift when she was called back. She drove at 175kph and stopped at no traffic lights to get back to the centre as quickly as possible.
"Chaos, that’s what I saw," she said of her arrival.
Dr Coates said that by the time he reached the hospital there were already more than 70 medical staff at work, and eight or nine surgeons helped evaluate patients to determine who was most in need of surgery. The most critically wounded sometimes had up to 20 people around their bed working on them.
"It was a trauma bay full of at least 70 people and patients stacked everywhere. It was controlled chaos," Dr Coates said. "At one time we had eight operating rooms going at the same time."
By early Monday afternoon, the trauma centre had received 104 patients, most with gunshot wounds. Four died, 40 were released, 12 were in critical condition and eight were in surgery. Some had crush injuries from being trampled.
“It was all hands on deck. Word travelled very fast. People were very proud to come in," said spokeswoman Danita Cohen.
Last year, the trauma centre had a training drill in which staff practised receiving patients after a fictional mass shooting at a concert. "This is what we do, we were prepared for this," Ms Mullan said.
It was a similar scene at Sunrise Hospital on the other side of town.
"I have never seen a scene like the one I just saw this morning," said Nevada congressman Ruben Kihuen, whose district includes parts of the Las Vegas area, when he visited Sunrise. "There were about 190 people taking up every single bed possible, every single room possible, every single hallway possible. Every single nurse, every single doctor from all over the city came and are assisting a lot of these victims."
Friends and relatives searched frantically for news of the injured, but the sheer volume of patients slowed the process. At Sunrise, Mr Kihuen said, more than 90 of the 190 patients had no identification.
Las Vegas police urged family members not to inundate local hospitals in search of the missing, and telephone hotlines were set up to help locate missing loved ones. Police asked those wanting to donate blood not to go to the hospitals where the staff were overwhelmed with patients, and directed them to clinics in the area instead.
Paul Hwangpo, a Las Vegas Uber driver, said he had spent the day ferrying tourists and residents to the clinics to give blood. One had a six-hour wait, the other four hours, he said.
Ms Mullan said that emotionally the most difficult moments were when it came time to fill out paperwork for patients known only as Jane or John Doe because they had no identification on them.
"When we have families coming up looking for loved ones and we have Does, that’s overwhelming. I’m human. I cry. I’m sad for the loss," she said.
But she was proud of the way hospital staff had responded to the emergency.
"I've been a nurse for 30 years, and on the most tragic moment I've ever been involved in I was most proud to be a nurse," she said.
Paddock, 64, a high-stakes gambler and retired accountant, killed himself as authorities stormed his hotel room at the Mandalay Bay hotel casino.
He had 23 guns — some with scopes — in the room where he had been staying since Thursday, four days previously. He knocked out two windows to create the sniper's perches he used to rain bullets on the crowd of 22,000 nearly 500 metres away.
He also had two "bump stocks" that can be used to modify weapons to make them fully automatic, according to law enforcement officials. At Paddock's home, the authorities found 19 more guns, explosives and thousands of rounds of ammunition. His car contained several kilos of ammonium nitrate, a fertiliser that can be turned into explosives.
The FBI discounted the possibility of international terrorism, even after ISIL claimed responsibility for the attack. But beyond that, the motive remained a mystery, with Sheriff Joseph Lombardo saying: "I can't get into the mind of a psychopath at this point."
His brother was equally mystified. When asked what might have motivated then Paddock, his brother Eric, who lives in Florida, replied, "I can't even make something up. There's just nothing."
While Paddock appeared to have no criminal history, his father was a bank robber who was on the FBI's most-wanted list in the 1960s.
President Donald Trump on Tuesday called the gunman "demented" and a "very, very sick individual." Asked about gun laws, the president said, "We'll be talking about gun laws as time goes on."