Las Vegas killer Stephen Paddock had an arsenal of 42 weapons and explosives, police have discovered, as detectives work to establish the motives behind the worst mass shooting in modern US history.
A detailed picture of the 64-year-old is starting to emerge as police try to determine why the gunman targeted concertgoers at Route 91 Harvest country music festival from his hotel window.
At least 59 people have been killed and more than 500 injured following the attack at about 10.20pm on Sunday local time.
Authorities found 23 weapons in Paddock's 32nd floor room of the Mandalay Bay Resort and Casino, in addition to 19 firearms, some explosives and thousands of rounds of ammunition, at Paddock's home in Mesquite.
Here's everything we know about the shooter so far:
Who is Stephen Paddock?
Stephen Paddock lived in a retirement community and was a multimillionaire real-estate investor who liked to travel to Las Vegas to play high-stakes video poker. His brother said he previously worked in accounting.
Paddock bought his house in Mesquite in 2015, according to USA Today. The Sun City Mesquite senior complex features 1,400 homes, an 18-hole golf course, swimming pools and a recreation center.
According to public records, Paddock owned two airplanes and had a private pilot's licence.
The 64-year-old had no criminal record and was not believed to be connected to any militant group, police said.
Despite so-called Islamic State claiming responsibility for the shooting, saying the "shooter converted to Islam months ago", Aaron Rouse, the FBI agent in charge in Las Vegas, said investigators saw no connection to international terrorism.
A senior US government official told Reuters that Paddock's name was not on any database of suspected terrorists.
Police said they believe Paddock was the "sole aggressor" and acted alone.
Paddock was not known to have served in the military, or to have suffered from a history of mental illness or to have registered any inkling of social disaffection, political discontent or radical views on social media.
But one US official said there was reason to believe that the shooter had a history of psychological problems, Reuters reports.
The attacker's motives remain a mystery, with Sheriff Joseph Lombardo saying: "I can't get into the mind of a psychopath at this point."
The closest Paddock appeared to have ever come to a brush with the law was for a traffic infraction, authorities said.
Paddock shot concertgoers from the 32nd floor of the Mandalay Bay Resort and Casino.
Paddock is reported to have smashed hotel windows prior to the shooting with a hammer-like device.
A law enforcement official said two rifles with scopes on tripods were found positioned in front of the broken windows.
A SWAT team blew open the entry to the 32nd floor room of the hotel and found the gunman dead.
Authorities found 23 weapons in the room, including assault-style rifles and some arms that may have been modified in an attempt to convert them into machine guns, Reuters reports.
The cache included AR-15-style and AK-47-style rifles and a large amount of ammunition.
Lombardo said a search of the suspect's car turned up a supply of ammonium nitrate, a fertiliser compound that can be formed into explosives and was used in the 1995 Oklahoma City bombing of a federal office building that killed 168 people.
Police found another 19 firearms, some explosives and thousands of rounds of ammunition at Paddock's home in Mesquite, totalling 42 weapons in Paddock's possession, Reuters reports.
Police also searched a second house connected to Paddock in Reno, Nevada, more than 400 miles (644 km) northwest of Las Vegas.
Chris Sullivan, the owner of the Guns and Guitars shop in Mesquite, issued a statement confirming that Paddock was a customer who cleared "all necessary background checks and procedures," and said his business was cooperating with investigators.
"He never gave any indication or reason to believe he was unstable or unfit at any time," Sullivan said. He did not say how many or the kinds of weapons Paddock purchased there.
Paddock had been registered as a guest at the hotel since September 28.
Asked if authorities believed the shooting was an act of terrorism, Lombardo replied: "No. Not at this point. ... We don't know what his belief system was at this time."
Police were seeking "a companion" of the shooter, named Marilou Danley, but have since located her. They have also found vehicles they were seeking.
Danley is believed to be an Australian citizen and of Indonesian decent.
Stephen Paddock's father was a convicted bank robber who used to be on the most FBI's most wanted list.
Patrick Benjamin Paddock was "diagnosed as psychopathic", according to a poster issued by law enforcement for the fugitive.
The suspect's brother, Eric Paddock, described Stephen Paddock as financially well-off and an avid enthusiast of video poker games and cruises.
The shocked sibling said the family were "dumbfounded" by the attack, adding: "We can't understand what happened."
"No affiliation, no religion, no politics. He never cared about any of that stuff," Eric Paddock said as he alternately wept and shouted. "He was a guy who had money. He went on cruises and gambled."
Stephen Paddock, who had worked previously as an accountant and never served in the military, was "not an avid gun guy at all," though he had a couple of handguns and a long gun, his brother said.
Eric Paddock also told The Associated Press that he had not talked to his brother in six months and last heard from him when Stephen checked in briefly by text message after Hurricane Irma.
Their mother spoke with him about two weeks ago, and when he found out recently that she needed a walker, he sent her one, Eric Paddock said.
"She's completely in shock," he said.
Public records offered no hint of financial distress or criminal history. Eric Paddock, who spoke with reporters outside his home near Orlando, Florida, said even if his brother had been in financial trouble, the family could have bailed him out.
Eric Paddock recalled receiving a recent text from his brother showing "a picture that he won $40 000 on a slot machine. But that's the way he played."
He described his brother as a multimillionaire and said they had business dealings and owned property together. He said he was not aware that his brother had gambling debts.
"He had substantial wealth. He'd tell me when he'd win. He'd grouse when he'd lost. He never said he'd lost four million dollars or something. I think he would have told me."