Hospitals near Aurora, Colorado, were flooded with victims after a movie theater shooting Friday morning.

An Aurora Fire Department call log reveals the urgency of the situation.

"If they're dead just leave them," a voice tells a fire department responder who reported that police said there may be a number of people dead inside the theater. "We're in a mass casualty situation at this time. Please make sure that you guys set up some kind of transport officer over there that can contact the hospitals so we don't overload one."

The emergency department at Denver Health Hospital was chaotic as staff prepared for the arrival of patients from the shooting, said Dr. Christopher Colwell, director of emergency medical services there. The hospital received seven victims, but called in extra personnel and was ready to take in more patients.

"You're not sure how they're going to arrive to you, so you prepare for the worst," he said.

Gunshot wound patients are fairly regular at Denver Health, although not on this scale, he said. In a mass shooting situation, staff assess the severity of the wounds and what steps must be taken -- some need to go straight to the operating room, others can wait, still others may not require surgery.

Colwell was a physician who treated victims at the scene of the Columbine High School shootings in 1999. Five patients were transferred to Denver Health; all survived.

"We have obviously done a lot of training exercises since then to try to prepare for an event like that," Colwell said.

Dr. Frank Lansville, medical director of emergency services at Aurora South Hospital, told CNN his hospital had seen 18 patients so far, 12 of whom suffered from gunshot wounds. There were several tear gas victims who were stable, he said. They had been seen, decontaminated and discharged. "The others had horrific gunshot wounds to various parts of their body," he said.

At Aurora Medical Center, the first victim of the movie theater shooting came in before the staff had even heard about the attack, said Tracy Lauzon, director of EMS and trauma services at the hospital.