The shooter with multiple machine guns who fired indiscriminately at crowd gathered for a music festival was a 64-year-old retired man with no criminal record.
Stephen Paddock, 64, was at first glance set for a quiet life in a desert retirement community, an hour's drive to Las Vegas, where he bought a new home in 2015.
His motives for carrying out what was the worst mass shooting in recent US history are unclear. Las Vegas Sheriff Joe Lombardo described the shooting as a "lone wolf" attack. "We have no idea what his belief system was," he said.
Public records point to an itinerant existence across the American West: a few years in coastal California, a few years in other parts of Nevada.
Paddock had a hunting licence in Texas, where he lived for at least a few years. He got his pilot licence, and had at least one single-engine aircraft registered in his name.
In early 2015, he bought a modest two-storey home in a new housing development for retirees on the dusty edge of Mesquite, a small desert town popular with golfers and gamblers that straddles the Nevada border with Arizona.
"It's a nice, clean home and nothing out of the ordinary," Quinn Averett, a Mesquite police department spokesman, told reporters on Monday. Some guns and ammunition were found inside, though nothing remarkable in a region where gun ownership is high.
An hour's drive southwest is Las Vegas, where Paddock would check into a 32nd-floor room last Thursday at the Mandalay Bay Resort and Casino with at least 10 rifles, and go on to kill at least 58 people and injure more than 500. Police said he killed himself as police stormed the hotel room.
Eric Paddock, the shooter's brother, said the family was "bewildered" as to what drove him to mass murder.
"He's a guy who lived in a house in Mesquite and drove down and gambled in Las Vegas", he told told CBS News.
“Not an avid gun guy at all...where the hell did he get automatic weapons? He has no military background,” gunman’s brother says pic.twitter.com/EMSKLQGYFM— CBS News (@CBSNews) October 2, 2017
He helped his brother move to escape Central Florida's humidity to Nevada in order to be able to play more video poker two years ago, Eric Paddock told the Orlando Sentinel. The two were last in touch a few weeks ago, texting about power outages after Hurricane Irma hit Florida.
A former neighbour named Sharon Judy in Viera, Florida, told the newspaper that Stephen Paddock was a friendly man who had described himself as a professional gambler. She said he showed her a picture of him winning a $20,000 slot-machine jackpot.
Paddock had no criminal record other than a traffic infraction, authorities said.
Another former neighbour said the suspect was a professional gambler and "weird".
Before moving to Mesquite, Nevada, he lived in another town called Mesquite in Texas. He was listed as the manager of an apartment complex.
The suspect's other brother, Bruce Paddock, told NBC his brother had made money through apartment buildings, which he owned and managed with his mother, who lives in Florida.
Eric Paddock told reporters their father was a bank robber who used to be on the FBI's most wanted list and once escaped from prison.
Records as recently as 2015 list Paddock as single. Police and public records said he lived with Marilou Danley in the Nevada retirement community.
Ms Danley described herself as a "casinos professional," as well as a mother and grandmother on social media websites.
She was travelling outside the country, and police say she had no connection with the attack, CNN reported. She was not with Paddock when he checked into the Mandalay, police said.