LAS VEGAS (AP) — Las Vegas investigators offered a new version of events Friday in a shifting timeline surrounding the deadliest shooting in modern U.S. history as they described how the gunman opened fire on nearby airport jet fuel tanks and on police officers arriving at the massacre.

Clark County Sheriff Joe Lombardo held a highly anticipated news conference alongside the top FBI agent in Las Vegas amid questions about whether police could have done more to stop gunman Stephen Paddock on Oct. 1.

They provided no new information about Paddock’s motivation as he killed 58 people and wounded more than 500 at a country music festival. Forty-five people remain hospitalized in critical condition, Lombardo said.

The sheriff said an autopsy has been performed on Paddock, and the coroner observed “no abnormalities” in his brain. He said the brain has been shipped to a facility to do a microscopic evaluation.

Lombardo confirmed that Paddock intentionally opened fire on jet fuel tanks at the nearby Las Vegas airport and said he took shots at arriving police officers, possibly to keep them at bay as police rushed to his room.

But nearly two weeks after the massacre, questions remain unanswered.

What drove Paddock to open fire on the country music festival? Police and the FBI say they’re still at a loss to explain his motive but said they have found no signs that he had ideologies or connections to any groups.

Why did Paddock stop firing into the concert? Authorities do not know, but police apparently had not reached his hotel room by that point.

In a chronology provided Monday, Lombardo had said Paddock started spraying 200 rounds from his suite into the hallway of the Mandalay Bay at 9:59 p.m. Oct. 1, wounding an unarmed security guard in the leg.

He said Friday that the security guard came to a barricaded stairwell door at 9:59 and wasn’t shot until around 10:05 p.m.

About that time, the gunman unleashed a barrage of bullets on the festival crowd. Then he killed himself with a gunshot to the head.

Lombardo’s newest version of events aligns with that Mandalay Bay officials said Thursday. They had disputed whether six minutes actually passed between the first shots in the hallway and the start of the concert rampage and said Paddock may have wounded the security guard within 40 seconds of firing into the crowd.

Earlier this week, lawyers had questioned why police and security weren’t able to stop Paddock sooner when authorities said six minutes passed between the bursts of gunfire.

Lombardo also pushed back against criticism of his office over whether more could have been done to stop the shooter.

“In the public space, the word incompetent has been brought forward. I am absolutely offended with that characterization,” he said.

The 10-minute attack on the crowd began at 10:05 p.m., when the 64-year-old real estate investor and retired accountant began firing more than 1,000 rounds from two bashed-out windows, police said. Police didn’t arrive on the 32nd floor until 10:17 p.m., two minutes after he had stopped shooting, according to Lombardo.

The wounded guard, Jesus Campos, used his radio to call for help, the statement said. A maintenance worker, Stephen Schuck, has said he also called for help on his radio, asking a dispatcher to call the police because someone was shooting a rifle on the 32nd floor.

It’s not clear what Mandalay Bay maintenance and security workers did with those messages by the guard and maintenance worker.

The timeline given by police earlier this week differed dramatically from the one they gave last week: that Paddock wounded Campos after he had opened fire on the crowd. Campos was called a hero whose presence outside Paddock’s suite stopped the concert carnage.

As authorities seek answers, they are lacking one important investigative tool. There are no surveillance cameras in the hallways at the Mandalay Bay.

The FBI, which is leading the investigation, again pleaded for the public’s help.

“We continue to ask you if you have factual information in furtherance of this investigation, please call us. If you know something, say something,” FBI Special Agent in Charge Aaron Rouse said.

Court officials on Thursday released copies of two search warrant applications that police submitted to a judge who approved a raid on Paddock’s home in a retirement community in Mesquite, Nevada. The documents list items that investigators were seeking, including guns, explosives, computers, medications and personal records.

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Associated Press writers Ken Ritter and Sally Ho in Las Vegas, Kate Brumback in Atlanta and Michelle Price in Salt Lake City contributed to this report.

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For complete coverage of the Las Vegas shooting, click here: https://apnews.com/tag/LasVegasmassshooting .