The Australian girlfriend of the Las Vegas mass shooter said he showed signs of mental illness - such as laying in bed and screaming, a new report reveals.

Marilou Danley revealed Stephen Paddock "would lie in bed, just moaning and screaming, 'Oh my God,'" according to an NBC News report citing former FBI officials briefed on the matter.

Ms Danley also said that Paddock showed "mental health symptoms," one of the unnamed officials said.

Investigators are struggling to figure out why Paddock, 64, went on the deadly spree that killed 58 and injured nearly 500 others.

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Marilou Danley, girlfriend of Las Vegas gunman Stephen Paddock.
Marilou Danley, girlfriend of Las Vegas gunman Stephen Paddock.

Police and the FBI are also investigating whether he planned a car bombing.

The chilling revelations came as new detail emerged yesterday about Paddock's lifestyle.

A former worker at the Atlantis Casino Resort and Spa in Reno, Nevada, where Las Vegas shooter Paddock frequently gambled, said he had a "god complex" and expected quick service no matter how busy employees were.

"It was just his demeanour. It was like, 'I'm here. Don't cross me. Don't look at me too long'," said former executive host John Weinreich.

Another gambler described him as "creepy".

It was here that Paddock met his Australian partner Ms Danley, 62, who has been described as "a person of interest" by investigators.

Community members hold candles as they attend a vigil for fallen Las Vegas Metropolitan Police Department Officer Charleston Hartfield at Police Memorial Park on October 5. Photo / AP
Community members hold candles as they attend a vigil for fallen Las Vegas Metropolitan Police Department Officer Charleston Hartfield at Police Memorial Park on October 5. Photo / AP

Ms Danley previously worked as a high roller hostess at the casino which is about a 20 minute drive from the Reno home they shared and were both last seen at in August.

They had another home in Mesquite, an hour northeast of Las Vegas. Both have been raided by police who found weapons and explosives.

Ms Danley was questioned in Los Angeles on Wednesday by the FBI and is understood to be staying in the city with her daughter, who lives in Venice Beach. Sheila Darcy Linton, 40, is an artist with a 7-year-old son.

The family home has been empty since media camped on their street from Monday, according to neighbours, who described Ms Linton and her husband Micah Linton as "just a normal family".

A makeshift memorial has been set up under the Welcome to Faboulous Las Vegas sign in the shadow of Mandalay Bay hotel. Photo / AP
A makeshift memorial has been set up under the Welcome to Faboulous Las Vegas sign in the shadow of Mandalay Bay hotel. Photo / AP

"They seem very nice. I feel sorry for them to have been thrust into this," said one neighbour, who did not wish to be identified.

Meanwhile, Las Vegas officials yesterday began releasing the bodies of the victims to their families, but warned it could be months before they learn exactly how their loved-ones died.

Clark County Coroner John Fudenberg said his staff had worked day and night to notify families that their loved ones had been killed.

"This has been very, very difficult," Mr Fudenberg said.

Employees had endeavoured to speak with as many as five family members per hour in recent days, he said.

The remains were slowly being released to local mortuaries, which have pledged to help both local and out-of-town families receive their loved ones and prepare them for funerals.

A woman pauses while looking at some of the 58 white crosses for the victims of Sunday night's mass shooting. Photo / AP
A woman pauses while looking at some of the 58 white crosses for the victims of Sunday night's mass shooting. Photo / AP

Paddock may have spent huge sums to amass his arsenal, but often spent just $US3.50 for a meal.

The 64-year-old went to the Mesquite Community and Senior Centre a few times a week to eat Mexican food, meat loaf and burgers, according to the Daily Mail.

And on the day he drove to Vegas to check in at the Mandalay Bay Resort and Casino, he dropped in at the government-run centre to ask the cook for an enchiladas recipe.

"We recognised Stephen when his face flashed up on TV," said local resident Marshall Meland, 78, who was enjoying lunch at the centre.

"He last came in to the centre around 11am last Thursday and checked in at the desk, but didn't stop for lunch like he usually does," he said.

"Instead, he went straight up to the counter to speak with the cook and asked her about an enchiladas dish she cooks - he wanted to know how she made it," Mr Meland said.

"After that he left. No one took any notice of him. It wasn't until later after what he did that we realised he drove to Vegas that afternoon. Everyone at the centre is shocked."

Other fellow diners remembered Paddock as an unsociable and quiet man who sat alone to eat his lunch.

Police and rescue personnel gather at the intersection of Las Vegas Boulevard and Tropicana Ave. after a mass shooting on October 2. Photo / AP
Police and rescue personnel gather at the intersection of Las Vegas Boulevard and Tropicana Ave. after a mass shooting on October 2. Photo / AP

A retired construction worker described him as "introverted."

"He'd come in on and off, sometimes up to three times a week," David Blake, 81, told the site.

"He's been coming in at least a year and when I first saw him I thought he was a homeless person, he was unshaven, dishevelled, quiet - he wasn't a big conversationalist," he said.

Blake added that Paddock's odd behaviour was not unusual in the gambling town.

"A lot of people who heavily gamble are like that, they're in a world of their own," he said. "They don't get a chance to have much of a social life. Stephen didn't seem to me like he was in to anything else other than deep thinking of how he was going to play his next poker game."