Las Vegas: Las Vegas gunman Stephen Paddock set up several cameras in his hotel room and one on a room service cart in the hallway capturing the arrival of officers, police say.

Paddock, 64, a retiree and multimillionaire gambler, opened fire on the Route 91 Harvest country music festival on Sunday night, local time, killing 59 people and injuring more than 500.

Over four days, he wheeled more than 10 suitcases into Room 32135 of the Mandalay Bay Resort and Casino, about 450 metres from the festival site, and unloaded a cache of 23 guns, ammunition, tripods and bump-stock devices to modify rifles to make them discharge ammunition more quickly.

On Wednesday, unverified leaked photos and video emerged on Twitter offering a glimpse inside the hotel room that unleashed the deadliest shooting in modern US history.

High-powered guns lie on the carpet among piles of bullets and a neat stack of 15 magazines. Another firearm sits in the hallway on a bipod, used for stability when firing at targets.

One photo shows the bottom half of a man's body lying on the floor, dressed in black pants, slip-on shoes and black gloves. The curtains are drawn in the dark room and on a nearby table, there is a slip of paper although police do not believe anything resembling a suicide note was left behind.

Footage obtained by the New York Post show double doors to the suite blown off their hinges and a room service cart in the hallway.

Las Vegas Metropolitan Police Sheriff Joe Lombardo did not verify the photos and said he was "troubled" by their release. He said an internal investigation into how they were obtained by journalists.

He confirmed that investigators found several cameras inside and outside the room, including one mounted on a room service cart with views down the hallway.

He did not believe that Paddock recorded or transmitted footage from the cameras but they might have been used to monitor the arrival of officers. 

"I anticipate he was looking for anybody to come and take them [sic] into custody," he said.

While no motive has been uncovered, Sheriff Lombardo said it was obvious that Paddock's massacre was premeditated and well organised.

"This individual was obviously premeditated. It was pre-planned extensively and I'm pretty sure he evaluated everything he did."

He said that a search of a home in Reno, Nevada, belonging to Paddock uncovered a further five handguns, two shotguns and a plethora of ammunition. 

Police found 19 guns, explosives and several rounds of ammunition in a home in Mesquite, Nevada, that Paddock shared with his girlfriend, Marilou Danley.

Sheriff Lombardo said police intended to interview Danley who he said was in the Philippines when she returned this week.

She is considered a "person of interest" although he gave no hint about what she may have already told investigators.

Danley, 62, an Australian-Filipina grandmother, was on a holiday with friends and family at the time of the shooting, MSNBC reported.

Lombardo later told a press conference Daley was in the Philippines, authorities were in contact with her and hoped to have more information soon.

She met Paddock about 2014 after she divorced her husband of 22 years, Geary Danley, and moved away from Reno. She lived in an over-55s community with Paddock in Mesquite.

New details emerged on Wednesday with MSNBC and CNN both reporting that Danley wired $US100,000 ($130,000) to the Philippines in recent weeks.

For years, Paddock had made millions as a professional gambler playing $US100 hands of poker, his brother Eric said.

It has emerged that Paddock was gambling huge sums of money in the days leading up to the massacre.

In two weeks, he had made 16 mandatory reports to federal authorities of casino wins above $US10,000 each day.