The site of the Route 91 music festival mass shooting is seen outside the Mandalay Bay Resort and Casino in Las Vegas.
LAS VEGAS - Police recovered a huge cache of guns and explosives on Monday from the Las Vegas hotel room and home of the man accused of killing at least 59 people and injuring over 500 in the deadliest mass shooting in US history.
Police said Paddock, a retired accountant with no criminal record, smashed windows in his 32nd floor hotel room shortly after 10pm and trained bursts of automatic weapons fire on thousands of people attending a country music concert below.
Investigators recovered at least 16 guns, including assault rifles, from Paddock's room at the Mandalay Bay hotel, and another 18 firearms along with bomb-making materials at one of his two homes.
The Islamic State group claimed that Paddock was one of its "soldiers" but the FBI said it had found no such connection so far and the local sheriff described him as a lone "psychopath."
Police said Paddock killed himself before a SWAT team breached his hotel room overlooking the country music venue.
Sheriff Joseph Lombardo said a security guard was shot in the leg as officers stormed the room where Paddock had been staying since 28 September.
He said a search of Paddock's house in Mesquite, Nevada, recovered "in excess of 18 additional firearms, some explosives and several thousand rounds of ammo."
Lombardo said investigators had discovered several pounds of an explosive called tannerite in the Mesquite home, as well as ammonium nitrate, a type of fertiliser, in the gunman's car.
The sheriff said the death toll had risen to 59, while 527 people had been injured.
- 'Lone wolf' -
Lombardo said the authorities had found no manifesto or anything else to explain Paddock's actions.
"This individual is a lone wolf and I don't know how it could have been prevented," he said. "I can't get into the mind of a psychopath at this point."
President Donald Trump denounced what he called "an act of pure evil" and said he would visit Las Vegas on Wednesday.
But the White House pushed back at calls to reopen the US debate on tighter gun controls.
"A motive is yet to be determined and it would be premature for us to discuss policy when we don't fully know all of the facts or what took place last night," Trump's spokeswoman Sarah Sanders said.
Lombardo said Paddock had apparently used some kind of hammer to smash the window of his hotel room before opening fire on the concert crowd of some 22,000 people.
CIA spokesman Jonathan Liu said "the Intelligence Community is aware of the claim of responsibility by a foreign terrorist organisation."
"We advise caution on jumping to conclusions before the facts are in," Liu said.
Paddock, according to his brother, was a high-stakes gambler and their bank-robber father was once on the FBI's 10 Most Wanted list.
But Eric Paddock stressed that his brother led an otherwise normal life, doting on their mother.
"He liked to play video poker. He went on cruises. He sent his mother cookies," he said.
"We're trying to understand what happened," his brother said. "We're lost."
Paddock had "no religious affiliation, no political affiliation" and was "not an avid gun guy at all," his brother added.
Paddock's girlfriend, a 62-year-old Asian woman named Marilou Danley, was out of the country at the time of the shooting.
Lombardo said she had been located in Tokyo, and would be questioned upon her return.