The gunman who killed dozens of people when he opened fire on the crowd of a Las Vegas country music festival had no abnormalities on the brain, an autopsy has revealed.
County Sheriff Joseph Lombardo said investigators were still awaiting results of a toxicology report on Stephen Paddock's body, which would show whether he was under the influence of drugs or alcohol when he began spraying revellers with bullets.
The 64-year-old gunned down 58 people and injured 489, before apparently killing himself.
Sheriff Lombardo told the Las Vegas Review-Journal that the results of an analysis of his brain revealed no abnormalities and therefore no clues as to what motivated his behaviour.
The results appear to quash circulating in the wake of the attack, that Paddock could have been suffering from a brain tumour or a mental disorder.
Police are still struggling to identify what drove the prolific gambler to carry out mass murder.
Sheriff Lombardo said he was “absolutely” confident authorities will find out what motivated him. But nearly two weeks on, investigators are still struggling to explain why he committed the worst mass shooting in US history
Officials said last week they believed Paddock was suffering from an undiagnosed severe mental illness but have so far ruled out any political or ideological motivation.
Kevin McMahill, of the Las Vegas Metro Police Department, told ABC News: “We thought we might find some ideology, some economic or political or social reason. Some medical reason. But we haven’t found it yet.”
Asked by a reporter if Paddock may have launched one of the biggest mass shootings in US history simply because he could, Mr McMahill didn't rule out the idea.
He said: “That’s certainly a possibility but it’s one of those possibilities you really can’t wrap your mind around. I don’t know if I can accept that.”
Paddock's girlfriend Marilou Danley also said she had no concerns about his mental health after she was cleared by authorities of playing any role in the attack.