Mandalay Bay Hotel Worker Stephen Schuck Warned Of Shooter Before Las Vegas Massacre

Crime scene tape surrounds the Las Vegas Mandalay Bay Resort and Casino on October 2 after a gunman killed 58 people and wounded hundreds of others at a concert. Mark Ralston/AFP/Getty

A worker at the Mandalay Bay hotel said Wednesday that he warned staff at the complex to report an active shooter before gunman Stephen Paddock launched his massacre on crowds at a music festival below the venue.

The revelation has added to doubts about the initial timeline given by authorities about what happened Oct. 1. They had said the assault began with Paddock opening fire on concertgoers at the Route 91 Festival.

But the new account alleges that an unarmed guard Jesus Campos—who was initially believed to have approached and been shot by Paddock during his massacre—was shot before the assault, with that gunshot heard by a maintenance worker.

"As soon as I started to go to a door to my left the rounds started coming down the hallway," Stephen Schuck said. "I could feel them pass right behind my head.

"It was kind of relentless so I called over the radio what was going on," he said. "As soon as the shooting stopped we made our way down the hallway and took cover again and then the shooting started again."

It has added to questions about the police response to the shooting, with delayed communication possibly extending the time that Paddock had to fire upon civilians from his sniper's nest on the 32nd floor of the Mandalay Bay, where he had an arsenal of 23 guns, scopes and surveillance cameras.

But whether the authorities could have arrived to stop Paddock opening fire on the crowds is unlikely, given the short time between the shooting of Campos and Paddock's subsequent hail of fire that included more than 1,000 bullets.

Police are still searching for a motive, but have ruled out a connection to the Islamic State militant group (ISIS), which claimed the attack the day after the assault.

Authorities changed the version of events on Monday, saying that Paddock opened fire on a security guard six minutes before he shot onto revelers, killing at least 58 people and injured more than 500. Campos called hotel dispatchers on his radio and helped to clear the rooms on the 32nd floor while he was injured.

The company that runs the Mandalay Bay hotel, MGM Resorts, said on Tuesday that it was disputing the new timeline.

"This remains an ongoing investigation with a lot of moving parts," MGM Resorts spokesperson Debra DeShong said in a statement. "As evidenced by law enforcement briefings over the past week, many facts are still unverified and continue to change as events are under review. We cannot be certain about the most recent timeline that has been communicated publicly."

Campos told ABC News: "I was just doing my job," but did not appear to say whether he was shot before or after Paddock's shooting rampage. Little is known about Campos, and why it was claimed that he was shot after the attack, rather than prior.

His union representative told Newsweek after the attack that he deserves to be awarded the Presidential Medal of Freedom, the highest civilian honor in the U.S.

"I would be thrilled...thrilled isn't even the right word," David Hickey, president of the International Union, Security, Police and Fire Professionals of America (SPFPA).