Police are working to establish the motive behind a mass shooting which left 59 people dead and another 527 injured at a Las Vegas concert.
Stephen Paddock appeared to be settling into a quiet life a few years ago when the 64-year-old apartment manager and avid gambler bought a home in a quiet Nevada retirement community about an hour's drive from the Las Vegas Strip and his beloved casinos.
The first call reporting shots fired came at 10:08 p.m. Sunday, and the gunfire didn't stop until at 10:19 p.m., Clark County Undersheriff Kevin McMahill said.
Investigators believe at least one of the guns functioned as if it were fully automatic, and they are now trying to determine if he modified it or other weapons to be capable of spitting out a high volume of fire just by holding down the trigger, people familiar with the case said.
"We have determined to this point no connection with an international terrorist group", Aaron Rouse, special agent in charge of the Federal Bureau of Investigation (FBI) field office in Las Vegas, told reporters.
Psychological issues has also been reported as a potential cause, but is yet to be confirmed.
Police found 23 guns in his hotel room, as well as firearms and explosives at his Nevada home.
In an often emotional interview, concertgoer Jonathan Smith recounted the aftermath of the horrific attack in which 58 people lost their lives in the mass shooting. "I barely slept last night thinking about this evil man living next door with a house full of guns", she said. He called the gunman "demented" and a "very, very sick individual".
"At the end of the day we aren't Democrats or Republicans, Whites or Blacks, Men or Women".
NBC reports that law enforcement officials were familiar with Paddock. Jennifer Lopez performances planned for Wednesday, Friday and Saturday at Planet Hollywood were postponed out of respect for the victims.
Off-duty Las Vegas area firefighters who were attending the country music festival when a gunman opened fire on the crowd say they immediately started setting up makeshift triage operations with concertgoers bringing them gunshot victims. One photo shows Paddock's legs, splayed on the floor near several weapons, apparently after he killed himself.
It is thought he moved between two windows in his suite as he carried out the attack.
"People were running and there was chaos".
Las Vegas police have called Marilou Danley, who returned to the United States late Tuesday, a "person of interest".
He said there could be a genetic component to the slaughter: Paddock's father was a bank robber who was on the FBI's most-wanted list in the 1960s and was diagnosed a psychopath. But for some reason, with his girlfriend away in Tokyo, his thoughts had turned to murder.
Background checks are done when people buy guns, but they are also allowed to sell them privately.
The retired accountant was not known to have served in the military or suffered from a history of mental illness or registered any inkling of social disaffection, political discontent or radical views on social media.