Stephen Paddock killed 58 people and injured hundreds more earlier this month when he opened fire on a crowd at a music festival in Las Vegas

No Abnormalities Have Been Found in the Las Vegas Shooter's Brain: Report

As of Tuesday, an autopsy had not found any abnormalities in Stephen Paddock‘s brain when he opened fire on a crowd at a Las Vegas music festival earlier this month, killing 58 people and injuring hundreds more, an official told the Las Vegas Review-Journal.

Las Vegas Sheriff Joe Lombardo told the paper in a Tuesday interview that he didn’t have any information about Paddock’s toxicology results, but that the autopsy was underway.

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Lombardo said Paddock’s motive in the mass shooting remained unclear, despite extensive investigation including contact with his entire “family tree.”

“We may never know,” Lombardo said. “All those things that you would expect to find, we have not found.”

Paddock’s girlfriend, who has been cooperating with authorities, told them she had no concerns about his mental health, according to the Review-Journal.

Authorities have said that on Oct. 1, just after 10 p.m., Paddock fired down onto a crowd of some 22,000 people at the Route 91 Harvest festival in Vegas from his 32nd-floor hotel suite at the nearby Mandalay Bay casino.

According to authorities, the gunfire continued off and on for about nine to 11 minutes. The shooting killed 58 and injured 489.

Paddock was found dead in his suite of a self-inflicted gunshot wound before midnight, as law enforcement closed in.

Although police have not determined a motive for the killing, investigators learned that Paddock was a retiree, a former accountant and high-stakes gambler whose father was a notorious, “psychopathic” bank robber who spent nearly eight years on the FBI’s most-wanted list.

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Image zoom Stephen Paddock

Lombardo said that authorities have also interviewed Paddock’s two ex-wives, according to the Review-Journal.

They’ve also learned that, in the days before the shooting, Paddock stayed in a separate room at the Mandalay Bay free of charge.

The investigation makes progress every day, Lombardo said.

“We have no intelligence or evidence the suspect was linked or had affiliation with any known terrorist groups or ideologies,” he previously said of Paddock, noting that “in coordination with the FBI’s Behavioral Analyst Unit, a comprehensive picture is being drawn as to the suspect’s mental state.”

“Currently we do not believe there is one particular event in the suspect’s life for us to key in on,” Lombardo said at a news conference on Monday. “We believe he decided to take the lives he did and he had a very purposeful plan that he carried out.”

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Criminal profiler John Kelly, who is unconnected to the case, told PEOPLE on Thursday that he believes Paddock was born a killer.

“What would drive somebody that is so methodical and structured in life to go insane in a very structured and methodical way?” wondered Kelly, who acknowledged that he never met the shooter.

“Paddock was a pathological gambler, psychopath and a sociopath,” he said. “He was predisposed from birth and childhood to harbor extreme internalized shame, low self-esteem, depression and aggressive anger.”