The gunman who unleashed the deadliest mass shooting in modern U.S. history first wounded an unsuspecting hotel security guard in a hallway who promptly radioed for help, according to a TV interview broadcast Wednesday with the guard and a hotel building engineer whose life he is credited with saving.

In his only public recounting of the Oct. 1 shooting that killed 58 people and wounded more than 500, guard Jesus Campos told Ellen DeGeneres on her talk show that he was heading down the hall after calling for a maintenance worker when he heard "rapid fire" gunshots through the nearby doors of Stephen Paddock's suite in the Mandalay Bay.

"At first, I took cover. I felt a burning sensation. I went to go lift my pant leg up, and I saw the blood," Campos said. "That's when I called it in on my radio that shots had been fired."

He didn't say what time that was.

The hotel engineer, Stephen Schuck, who was sent to check a fire exit door that Campos found bolted shut, told DeGeneres that he didn't hear gunfire when he reached the opposite end of the 32nd floor hallway. Then, he heard what he thought was the sound of construction.

"I didn't know it was shooting. I thought it was a jackhammer," Schuck said. "And, you know as an engineer, I'm like, 'We're not working up here this late at night.' We wouldn't be doing that."

"It was, I believe, outside," he said, referring to gunfire that authorities say Paddock rained down from broken windows into a crowd of 22,000 at a country music festival. "It wasn't in the hallway yet."

Schuck said Campos leaned out from a door entrance and yelled for him to take cover.

"Within milliseconds, if he didn't say that, I would have got hit," Schuck said, describing bullets whizzing past his head.

Police later said more than 200 shots were fired into the hallway.

Campos, who walked into the interview with a cane, is recovering from a leg wound. Schuck wasn't injured. Both are on paid leave from their jobs, according to officials at MGM Resorts International, which owns the hotel.

The company, police and the FBI declined to comment on the TV appearance.

Campos drew intense attention when police hailed him as a hero just after the shooting, saying he unwittingly stopped the massacre by arriving in the hallway.

The police timeline changed dramatically a week later, when authorities said Campos reported being wounded at 9:59 p.m. — six minutes before people in the concert crowd reported shots.

The timeline of the massacre changed again last Friday, when Clark County Sheriff Joe Lombardo said Campos had been dispatched to the 32nd floor at 9:59 p.m. and was wounded in the hallway less than a minute before the massacre started at 10:05 p.m.

Schuck's account in the DeGeneres interview seemed to support that chronology.

He told Campos in the interview that the guard saved Schuck's life, and DeGeneres credited Campos with also warning a woman who started to come out of her room to get back inside.

"Shortly after that is when Stephen (Schuck) was approaching, and I told him to stay back and get cover, and that's when more rounds were dispersed," Campos said.

His interview came after the last-minute cancellation of a scheduled live interview with Fox host Sean Hannity last Thursday, said David Hickey, president of Security, Police and Fire Professionals of America.

Campos then dropped from public view, said Hickey, who had been involved in booking the appearance.

"We're more than pleased that he's resurfaced and appears to be in good health," Hickey said. "If he comes back as a security officer at Mandalay Bay, we'll see him again. If not, we wish him the best."