US authorities are delving into the psychology of the man who killed 58 people at a Las Vegas music festival, with the chief police investigator describing a “narcissist” who feared losing his high-rolling gambler status.

Clark County Sheriff Joe Lombardo said the investigation into the October 1 massacre had entered its second month, bringing clues, but nothing definitive as to what drove mass-murderer Stephen Paddock.

The investigator said Mr Paddock had lost a “significant” amount of wealth in the two years prior to the meticulously planned attack.

“This individual was status driven based on how he liked to be recognised in the casino environment and how he liked to be recognised by his friends and family,” Sheriff Lombardo said in a wide-ranging interview with CNN affiliate KLAS.

“Since September 2015, he’s lost a significant amount of wealth, and I think that might have been a determining factor on what he was determined to do.”

Mr Paddock’s family has also made headlines, including his estranged brother who was arrested on child pornography charges last month.

The father of Stephen Paddock, Benjamin Paddock, was also a notorious bank robber and jail-breaker who spent years on the FBI’s most-wanted list.

However, Sheriff Lombardo admitted the motive of the 64-year-old killer remained largely a mystery.

“There was something that popped his trigger or caused him to go into that direction and we have yet to determine what that is,” Mr Lombardo said.

“I hope we find something in the pathology of his brain that helps us understand this.”

The sheriff described Mr Paddock as a “lone actor” with a “psychotic mind” in the hour-long interview with KLAS journalist, George Knapp.

He added Mr Paddock had no links to extremist groups and the only political statement he was known to have made was that “he was happy with Trump because the stock market was doing well”.

He said Mr Paddock still had access to more than 4000 rounds of ammunition and had the ability to “do more harm” after unleashing 1000 rounds of bullets on concertgoers from the 32^nd flood of the Mandalay Bay hotel.

Mr Lombardo said he was convinced the mass-murderer took his own life because he was aware of police presence.

The sheriff said he believed Mr Paddock was assessing the crowd and noted the shooter had also set up video monitors to provide a view into the hallway outside his hotel room.

“I honestly believe that he believed the wolf was at the door.”

Investigators are continuing to interview Mr Paddock’s girlfriend, Marilou Danley, who has told authorities she knew nothing of her boyfriend’s plans.

Mr Lombardo told interviewer Mr Knapp he ”personally” struggled to believe Ms Danley’s account, noting Mr Paddock had purchased dozens of guns and weapons.

“You would think that Ms Danley would have some information associated with that,” he said. “But currently we haven’t been able to pull that out of her … if it’s in her.”