Police have named Stephen Paddock as the suspected gunman who killed at least 50 people and hospitalised more than 400 others at a Las Vegas concert.
The 64-year-old, of Mesquite, Nevada, sprayed bullets at music-lovers as a gig by country singer Jason Aldean was ending on Sunday night, said officers.
The suspect opened fire from a room on the 32nd floor of the Mandalay Bay Hotel and Casino.
Paddock killed himself at the scene as officers closed in.
It is the deadliest shooting in modern US history, with the death toll surpassing the 49 killed at a nightclub in Orlando, Florida, in June 2016.
Las Vegas Sheriff Joseph Lombardo said investigators found “in excess of 10 rifles” in the hotel room that Paddock checked into on 28 September.
He said the suspect turned a gun on himself as police approached the suite.
“We have no idea what his belief system was,” Sheriff Lombardo added.
The sheriff was asked if there was any evidence the attack was related to terrorism.
“No, not at this point,” he replied.
So-called Islamic State later claimed to be behind the attack, saying that Paddock had converted to Islam some months ago.
But the group provided no evidence for this and has made unsubstantiated claims in the past.
Senior US officials discounted the group’s statement.
Audio recorded at the concert indicates Paddock may have used an automatic rifle in the attack on the crowd of 22,000 people.
He had no prior “derogatory” interactions with police, said Sheriff Lombardo, except for one citation several years ago which the sheriff declined to specify.
Investigators have searched his two-bedroom home, which is part of a retirement community about one hour from Las Vegas.
Quinn Averett of Mesquite Police said it was a “nice, clean home, nothing out of the ordinary”.
He added he believed there were some weapons and ammunition found inside.
Authorities earlier appealed for help in locating Paddock’s roommate, Marilou Danley.
But investigators later said she had been interviewed, and was “no longer being sought out as a person of interest”.
Ms Danley, 62, was not with him when he checked into the Mandalay, officers said.
Investigators said she had been traced outside of the US.
They said Paddock “was utilising some of her identification”.
Eric Paddock, the suspect’s brother, described her as the gunman’s “girlfriend”.
“It’s like an asteroid just fell on top of our family,” he told the Las Vegas Review-Journal.
“There is no reason we can imagine why Stephen would do something like this,” he continued.
He told reporters his brother was “not an avid gun guy at all”.
“The fact that he had those kind of weapons is just… where the hell did he get automatic weapons?
“He has no military background or anything like that.
“He’s a guy that lived in a house in Mesquite, drove down and gambled in Las Vegas. He did stuff, eat burritos.”
In 2012, Paddock filed a negligence lawsuit against The Cosmopolitan resort in Las Vegas, after a fall caused by an “obstruction” on the floor, according to his brother.
The lawsuit was dropped by both parties in 2014.
Paddock had a licence to fly small planes, and owned two aircrafts, NBC reported.