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A hotel maintenance worker says he barely escaped unscathed when Las Vegas shooter Stephen Paddock opened fire down a hallway — and credited a hotel security guard with saving his life.

"When the first shooting started, I was kind of frozen for a second," worker Stephen Schuck said Wednesday on "TODAY." "He yelled at me, 'Take cover! Take cover!' If he yelled a second too late, I would have been shot."

Schuck said he came upon security guard Jesus Campos, who was unarmed and injured in his leg, as Paddock fired more than 200 bullets into the hall and nearby rooms at the beginning of his deadly rampage on Oct. 1. "I am incredibly blessed that somehow I came out of there alive," Schuck added.

His dramatic account, and the release of audio of those initial shots, comes amid a dispute over the timeline of the events and questions as to how quickly Las Vegas police could have learned about the massacre on an outdoor music festival.

In detailing a revised tick-tock of the shooting, Clark County Sheriff Joe Lombardo told reporters Monday that Campos was alerted to the 32nd floor of the Mandalay Bay Resort and Casino, where an alarm associated with a fire exit door went off.

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That was the same floor that Paddock, 64, had set up his cache of weapons amid his plan to fire from his hotel suite windows onto a crowd at a country music festival across the street, police said.

Suddenly, a hail of bullets came flying down the hall where Campos was, and the guard was injured at about 9:59 p.m., Lombardo said. Six minutes later, at 10:05 p.m., Paddock fired the first shots on concertgoers.

Previously, police had said Campos was hit after the attack on the crowd.

Schuck said the gunfire in the hallway was relentless and he "could feel them [the rounds] pass right behind my head." He said he took cover until the shooting stopped and he could reach Campos, then he radioed for help.

Lombardo said the shooting finally stopped 10 minutes later, at 10:15 p.m.

A police SWAT team got to the 32nd floor at 10:17 p.m., and a minute later learned that the security guard was hit and where the shots were fired from.

The police's latest timeline means it took 19 minutes for Las Vegas police to know what the guard and the maintenance worker already knew — where exactly Paddock was shooting from.

In that time, Paddock was able to kill 58 people and wound nearly 500 others in the worst mass shooting in modern U.S. history.

MGM Resorts, which owns the Mandalay Bay, said in a statement that it cannot comment about the ongoing investigation, but raised questions about the timeline since "many facts are still unverified."

"We cannot be certain about the most recent timeline that has been communicated publically (sic), and we believe what is currently being expressed may not be accurate," said MGM Resorts spokesperson Debra DeShong.

A motive for the carnage remains unclear and while police said they recovered a document with numbers on it in Paddock's hotel room, Lombardo on Monday declined to say what it meant.

Multiple law enforcement sources previously told NBC News it is believed to be calculations of shooting ranges, drop, and distance for higher precision in shooting into the concert crowd.

Lombardo added that the FBI's Behavioral Analysis Unit was compiling a comprehensive picture of Paddock, a known high-stakes gambler who was once prescribed Valium "for anxiousness."

"Currently, we do not believe there is one particular event in the suspect's life for us to key on," he said.