Rick Neale and John Bacon

USA TODAY Network

ORLANDO — Physicians at Orlando Regional Medical Center on Tuesday detailed the scramble to save lives in an overwhelmed emergency room following the shooting spree at a gay nightclub that left 49 people dead and dozens more struggling to survive.

Six victims of Sunday's massacre remained in critical condition, officials said. Twenty-one others also remained hospitalized. The gunman was killed by police at Pulse, which was crowded with dancing revelers on Latin Night.

"I will be surprised if we don't see the death toll rise" or see patients left with long-term injuries, physician Michael Cheatham said at a news conference at the hospital.

"There is no question that nurses saved lives" in the grueling hours as victims poured into the emergency room," Cheatham said.

Hospital trauma director Joseph Ibrahim likened the situation to “a war scene” with “patients in every corner." Surgeon Chadwick Smith said he was on duty when shooting victims began arriving at the hospital shortly after 2 a.m. Victims were dropped off via ambulances, police cruisers, trucks and private vehicles.

"They were coming in non-stop," Smith said of the victims. He began calling in more physicians: "I said 'This is not a drill, this is not a joke.'"

Nurses and technicians also rolled in. Smith said he worked triage, ranking patients based on the severity of their injuries.

"I just cannot say enough about how much we increased our resources to the level of need in a very short period of time," he said.

Obama: Calling ISIL 'Islamic extremists' would accomplish nothing

Orlando vigil: 'We are tired of massacres'

Survivor Angel Colon thanked the hospital staff for the care he was provided. He also described the horrifying moments at Pulse when the shooting began. He said he and his friends were wrapping up the night of partying with hugs when gunshots rang out.

"We grabbed each other and started running," Colon said. "I was shot three times in my leg and fell down."

Fleeing patrons trampled him, he said, and his leg was shattered. When the shooter went into another room Colon hoped someone would stop him, but minutes later the gunman returned, shooting people where they had fallen to ensure they were dead.

"He shoots the girl next to me, and I’m laying down, I’m thinking, ‘I’m next. I’m dead,’” Colon recalled. The gunman, identified as Omar Mateen, fired twice at Colon. He said he was hit in the hand and the hip.

"I was prepared to stay there, laying down down so he won't know I'm alive," Colon said. Later, a police officer grabbed him and dragged him out, he said.

Orlando victims: Their stories

The investigation into the attack, the deadliest mass shooting in U.S. history, continued Tuesday.

Sources told various news organizations that Mateen's wife, Noor Salman, may have known of her ex-husband's plans.

"It appears she had some knowledge of what was going on," Reuters quoted U.S. Sen. Angus King, a Maine Independent, as telling CNN. "She definitely is, I guess you would say, a person of interest right now and appears to be cooperating and can provide us with some important information," said King, a member of the Senate Intelligence Committee.

President Obama reiterated that there is no indication Mateen, who pledged allegiance to Islamic State in a 911 call, directly communicated with Islamic State militants.

"It is increasingly clear that the killer took in extremist information and propaganda over the Internet," Obama added, calling Mateen "an unstable young man who became radicalized.”

He again called for "common sense steps" to curb gun access. "People who aren't allowed on a plane shouldn't be allowed a gun," he said.

Obama also took aim at presumptive GOP presidential nominee Donald Trump, chastising political rhetoric such as squabbling over use of terms such as radical Islam. "Yapping," he said, won't win the war on terror.

In Port St. Lucie, the gun shop owner who sold weapons to the Orlando nightclub shooter, says Mateen passed a background check and bought two guns about a week apart.

"An evil person came in here and they legally purchased two firearms from us, and if he hadn’t purchased them from us, I’m sure he would have gotten them from another local gun store,” said Ed Henson, owner of St. Lucie Shooting Center.

Although Henson did not say whether the guns were used in the massacre, an Orlando Police Department news release indicates the Sig Sauer semiautomatic rifle and Glock 17 handgun used in the shooting were purchased within the past two weeks.

“This man held multiple security licenses; he had an armed and an unarmed license,” Henson said.

Pulse patrons: Mateen hung out at the club 'for years'

Several regulars at Pulse said Mateen, 29, patronized the club before the attack. One recalled seeing the gunman drink at the bar and another said he had used a gay dating and chat app.

A federal law enforcement official told USA TODAY investigators believe Mateen was in the Orlando area for several days prior to the shooting, suggesting he carefully considered the target.

The official, who is not authorized to comment publicly, said investigators are reviewing Mateen’s possible consideration of other iconic targets in the Orlando area, including Disney World. That review was ongoing and it was not immediately clear how seriously other locations were considered, the official said.

The owner of another Orlando LGBT club said he got a Facebook friend request last week from Mateen, according to reports from WKMG TV. Owner Michael Bass says he rejected the friend request when none of Mateen's friends seemed connected to an LGBT club, the station reported.

Orlando Police Chief John Mina has said the investigation, being led by the FBI, would include an effort to determine whether any victims were shot by police in the chaos of the final assault.

Contributing: Will Greenlee, USA TODAY Network