Hotel workers at the Mandalay Bay didn't call police until after Stephen Paddock opened fire on hundreds of concert-goers below despite knowing someone had already been shot, according to new phone records.

After hero security guard Jesus Campos was shot he reportedly called down to his superiors, but for some reason nobody called the police.

An anonymous source reviewed the new phone records on ABC's 'World News Tonight,' in an attempt to shed more light on an increasingly confusing timeline of events which saw more than 59 people killed and hundreds more wounded.

Additionally, security staffers didn't call police when a Mandalay Bay maintenance engineer Stephen Schuck called down to tell them Paddock was firing at him.

'Call the police, someone is firing a gun up here. Someone is firing a rifle on the 32nd floor down the hallway, he can be heard saying on new audio tapes released by the hotel on Wednesday.

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Engineer Stephen Schuck (pictured) said he was checking out a report of a jammed fire door on the 32nd floor of Mandalay Bay when he heard gunshots and saw shot security guard Jesus Campos, who told him to take cover

Stephen Paddock (pictured) shot a security guard in the Mandalay Bay hotel minutes before firing on revelers - not after he had been firing on the crowds for 10 minutes, cops said Monday

Clark County Sheriff Joe Lombardo, left, with Aaron C. Rouse, special agent in charge for the FBI in Nevada, discusses the Route 91 Harvest festival mass shooting on Monday

Schuck told told NBC News that he was checking out a report of a jammed fire door on the 32nd floor of Mandalay Bay when he heard gunshots and hotel security guard, Jesus Campos, who had been shot in the leg, peeked out from an alcove and told him to take cover.

'As soon as I started to go to a door to my left the rounds started coming down the hallway,' 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.'

Police said Monday they believe gunman Stephen Paddock shot a hotel security guard through the door of his suite six minutes before he unleashed a barrage of bullets into the crowd of concert-goers, killing 58 people and injuring hundreds more.

The injured guard used his radio and possibly a hallway phone to also call hotel dispatchers for help.

That account differs dramatically from the one police gave last week when they said Paddock fired through the door of his room and injured the unarmed guard after shooting into the crowd.

The company that owns Mandalay Bay has questioned the new timeline.

'We cannot be certain about the most recent timeline,' said Debra DeShong, a spokeswoman for MGM Resorts International. 'We believe what is currently being expressed may not be accurate.'

Las Vegas police did not respond Tuesday night to questions about the hotel's statement.

'Our officers got there as fast as they possibly could and they did what they were trained to do,' Las Vegas assistant sheriff Todd Fasulo said earlier Tuesday.

Windows of the Mandalay Bay hotel room from where Stephen Paddock launched his assault on concert goers

Guard Jesus Campos approached Paddock's room down the corridor, investigating an alarm - likely due to Paddock tampering with the doorway to the stairwell next to his suite. Paddock then fired on him at 9:59pm, and opened fire on people below at 10:05pm

Flowers, candles and other items surround the famous Las Vegas sign at a makeshift memorial for victims of the mass shooting

Gunshots can be heard in the background as Schuck reported the shooting on his radio, telling a dispatcher: 'Call the police, someone's firing a gun up here. Someone's firing a rifle on the 32nd floor down the hallway.'

It was unclear if the hotel relayed the information to Las Vegas police, who did not respond to questions from The Associated Press about whether hotel security or anyone else in the hotel called 911 to report the gunfire.

Joseph Giacalone, a professor at John Jay College of Criminal Justice and a retired New York City police sergeant, said the new timeline 'changes everything.'

'There absolutely was an opportunity in that time frame that some of this could've been mitigated,' he said.

Nicole Rapp, whose mother was knocked to the ground and trampled at the country music concert said she's 'having a hard time wrapping my head around' why police changed the timeline of the shooting.

'It's very confusing to me that they are just discovering this a week later,' she said. 'How did we not know this before? It's traumatic for the victims and their families not to be sure of what happened.'

ORIGINAL TIMELINE This is the original timeline of events given out by police on Wednesday. 10:05pm: Paddock fires his first shots on the crowd, as seen on CCTV. 10:12pm: First two officers arrive on the 31st floor and announce gunfire is coming from directly above them. 10:14pm: Guard Jesus Campos approaches Paddock's room and is shot, but only injured. 10:15pm: The last shots are fired from the suspect, per bodycam, due to Campos' intervention. 10:17pm: The first two officers arrive on the 32nd floor from the 31st. 10:18pm: Campos tells the cops he was shot and gives them the exact location of the suspect's room. 10:26-10:30pm: With Paddock quiet, eight additional cops arrive and they decide to evacuate the rooms on the floor. 10:55pm: Eight officers arrive in the stairwell next to the suspect's room and find the door tampered with and a camera on a room service cart outside; they decide to hold off. 11:20pm: Paddock's room is breached and police enter the room to find him dead. Advertisement

NEW TIMELINE This is the new timeline given out on Monday. 9:59pm: Campos approaches Paddock's room looking for an alarm going off at a door nearby - likely from the stairwell. He is shot at and injured. He immediately notifies hotel security. Stephen Schuck appears to back up this account 10:05pm: First shots fired by suspect. 10:12pm: First two officers arrive on the 31st floor. 10:15pm: The last shots are fired from the suspect for reasons unknown. 10:17pm: The first two officers arrive on the 32nd floor from the 31st. 10:18pm: Campos, who has been stricken for almost 20 minutes, tells police about Paddock's room. 10:26-10:30pm: With Paddock quiet, eight more cops arrive and they decide to evacuate the rooms on the floor. 10:55pm: Eight officers arrive in the stairwell next to the suspect's room and find the door tampered with and a camera on a room service cart outside; they decide to hold off. 11:20pm: Paddock's room is breached and police enter the room to find him dead. Advertisement

The six minutes that passed between the hallway shooting and the start of the shooting into the crowd wouldn't have been enough time for officers to stop the attack, said Ron Hosko, a former FBI assistant director who has worked on SWAT teams.

Rather than rush in without a game plan, police would have been formulating the best response to the barricaded gunman, he said.

'Maybe that's enough time to get the first patrolman onto the floor but the first patrolman is not going to go knock on that customer's door and say 'What's going on with 200 holes in the door?'' Hosko said.

Undersheriff Kevin McMahill defended the hotel and said the encounter that night between Paddock and the security guard and maintenance man disrupted the gunman's plans.

Paddock fired more than 1,000 bullets and had more than 1,000 rounds left in his room, the undersheriff said.

'I can tell you I'm confident that he was not able to fully execute his heinous plan and it certainly had everything to do with being disrupted,' McMahill said.

He added: 'I don't think the hotel dropped the ball.'