(AP) -- The first victim of the nightclub shooting arrived shortly after 2 a.m. and was relatively stable, giving doctors on the overnight shift hope that any others would not be severely wounded.

Then five more came, in much worse shape, and then more and more, until even hardened trauma surgeons and nurses were brought to tears by the sight of so many bleeding people lining up in the emergency room.

"They were dropped off in truckloads, in ambulance-loads," said Dr. Kathryn Bondani. The hospital ran out of ambulances, so firefighters, police and truck-driving citizens ferried the injured.

The trauma bay quickly overflowed with patients with serious gunshot wounds. Doctors did triage, moving critically injured people elsewhere and focusing on those whose lives were most in danger.

Luckily, the Pulse nightclub isn't far from Orlando Regional Medical Center, the region's main trauma hospital. But the emergency room staff usually gets advance word when severe cases are on their way. This time, victims started arriving within minutes after the shooting started, and the staff had to scramble.

Choking up a bit, the attending trauma surgeon on call that night, Dr. Chadwick Smith, described at a news conference on Tuesday how he called for reinforcements.

"I said, 'please come, please come. We need your help,'" Smith said.

"This is not a drill. This is not a joke," he told them. "'I need you as fast as I can.' Every answer I got was, 'I'll be right there.'"

Nurses and technicians also arrived, many without being told to come. Doctors quickly expanded from two operating rooms to six, performing surgery after emergency surgery. Another eight operations were scheduled for Tuesday.

Trauma surgeon Dr. William Havron arrived to see the hospital flooded with bloody victims with severe wounds. He called it "surreal."

"We were just given patient after patient after patient," Havron said. "We'd literally walk from that operation room to another operating room and just do it again and again."

Dr. Joseph Ibrahim said it looked like a "war scene" with "patients in every corner." Some had wounds from both large and small ammunition, suggesting the gunman used both his assault rifle and pistol.

Angel Colon, 26, was shot three times in his leg, and his bones shattered as he was trampled in the crowd. Then he was hit again, in the hand and hip, as the gunman shot the injured, apparently "making sure they're dead." Later, as a policeman dragged Colon to safety, his body was cut by shards of broken glass.

Appearing in a wheelchair, Colon turned to the doctors and nurses and said: "I will love you guys forever."

Others weren't ready to talk publicly. Felipe Marrero, 30, survived four shots in the back, and was barely able to sit up for a "selfie" with his friend Joseph Rivera, 24, who was able to reunite with him at the hospital Monday night.'

The trauma center is used to handling four or five patients a shift. A total of 44 arrived that night. Nine of them were too far gone to be saved, said Dr. Michael Cheatham, a critical care surgeon.

Of the rest, 27 remained hospitalized Tuesday, including six in intensive care, one of whom was shot in the head. Two patients in the ICU may be permanently disabled, but no patient has succumbed since the nine who were pronounced dead on arrival, Cheatham said.

Doctors said 12 victims were treated and six remain hospitalized at Florida Hospital Orlando, including Angel Santiago Jr., who was shot in the left foot and right knee as he huddled in one of the nightclub's bathrooms. He was stabilized with two units of blood, and expressed deep gratitude to the staff.

"I don't even know how I'm alive today," Santiago said.

The numbers are very fluid, with some victims still coming in to hospitals for treatment, Cheatham said.

"It was singularly the worst day of my career and the best day of my career," Smith said. "And I think you can say that of pretty much every person standing up here."