Stephen Paddock 'used to lie in bed screaming and may have been in mental anguish'

Police are still searching for a motive in the mass shooting

Stephen Paddock's girlfriend recalls the Las Vegas shooter lying in bed screaming to himself, reports claim.

Investigators believe the shooter may have been in “physical or mental anguish,” a former FBI official who was briefed on the investigation told NBC News. Another said the shooter displayed "mental health symptoms”.

"[His girlfriend] said he would lie in bed, just moaning and screaming, 'Oh, my God,'" one of the officials recalled.

Paddock was prescribed an anti-anxiety drug in June. Employees at a Starbucks near his Reno home recall him berating his girlfriend in public. But investigators do not believe his mental health was poor enough to have triggered an attack of this scale, the officials told NBC.

Last weekend, Paddock opened fire on a country music concert from his 32nd-story hotel window, shooting more than 500 people before killing himself. The new details about his mental state may provide hints as to the motive for the shooting, which police are still struggling to determine.

“In the spirit of the safety of this community or anywhere else in the United States I think it’s important to provide that information, but I don’t have it,” Clark County Sheriff Joseph Lombardo said in an interview on Thursday. “We don’t know it yet.”

Police had hoped Paddock’s girlfriend, Marilou Danley, would be able to provide some insight. But Ms Danely told investigators she knew nothing about Paddock’s plans for the attack. Through an attorney, she described Paddock as a “kind, caring, quiet man”.

“He never said anything to me or took any action that I was aware of that I understood in any way to be a warning that something horrible like this was going to happen,” she said.

Paddock’s brother, Eric Paddock, was similarly confused.

“Something had to happen to Steve – I'm not even trying to excuse it – but something happened that drove him into the pit of hell and he did this,” he told CBS.

A man on the Las Vegas Strip films on his phone the two broken windows of the Mandalay Bay hotel from which killer Stephen Paddock let loose (ROBYN BECK/AFP/Getty Images)

Investigators have discovered a note in Paddock’s hotel room that they are still analysing for significance. They do not believe it was a manifest or a suicide note, according to Mr Lombardo.

Authorities told NBC that Paddock may have also scouted other locations in Chicago and Boston before his attack. A Chicago hotel overlooking popular music festival Lollapalooza confirmed to The Independent that someone named Stephen Paddock had booked a room during the festival, but failed to show up.

For now, however, authorities are still at a loss for what could have motivated his killing spree. Answering reporters' questions on Monday, Mr Lombardo seemed frustrated.

"I can't get into the mind of a psychopath at this point," he said.