Crime scene photos have been leaked showing the firearms and the gunman's premeditated set-up that caused carnage across Las Vegas on Sunday.
- Pictures from inside Paddock's hotel room leaked
- Police say Paddock's massacre pre-planned
- Paddock's girlfriend named person of interest
Stephen Paddock smashed two windows of his suite on the 32nd floor of Mandalay Bay Resort and Casino and created a sniper's perch and directed at least two firearms at tens of thousands of people attending the Route 91 Harvest Festival.
The 64-year-old killed 58 people and injured more than 500, making it the most deadly massacre in modern US history.
Police found 23 firearms in the hotel room, including AK47s, a Colt AR-15 and three FN-15 rifles, and photos leaked to German newsmagazine Bild show the weapons Paddock dropped on the floor before he killed himself.
When police stormed the hotel room, they found the dead suspect along with firearms with calibres ranging from .308 to .223.
Gunman's hidden cameras
Paddock checked into the hotel four days prior, using the ID of his girlfriend, Marilou Danley.
He smuggled the 23 weapons into the hotel room in at least 10 suitcases, which he carried in over the four-day period.
Footage of Paddock's planned out surveillance also emerged. He set up a camera on what appeared to be a room service cart in the hotel hallway.
A cord can be seen running out from under a dirty dish and down under a hotel room door.
The surveillance was set up to warn him when police were getting close.
Las Vegas Metropolitan Department Sheriff Joe Lombardo told a media briefing on Tuesday there were cameras inside and outside the hotel room.
"I anticipate he was looking for anybody coming to take him into custody," he said.
"The FBI took all digital and electronic evidence and we are evaluating."
Pictures inside the room show he created a closed-off couch by pushing together two one-seater chairs.
One of the leaked photos shows a firearm resting on the makeshift couch, with the gun barrel peeking over the back of one of the chairs.
One of his 10 suitcases can be seen open on the floor behind the chairs.
In another image, two large firearms are seen resting on the floor next to ammunition and a hammer.
Inside Paddock's hotel room were also a pen and a piece of paper resting on a small table.
Another picture shows the door to the hotel room, barricaded by yellow police tape.
One side of the double doors is missing and on the floor inside the suite is another weapon.
Mr Lombardo said Paddock's attack was premeditated and authorities were looking into whether or not he had other sinister plans.
During the Sunday night rampage, a hotel security guard who approached the room was shot through the door and wounded in the leg.
"The fact that he had the type of weaponry and amount of weaponry in that room, it was pre-planned extensively," Mr Lombardo said.
"And I'm pretty sure he evaluated everything that he did and his actions, which is troublesome."
Mr Lombardo was also concerned images from inside the hotel room had been leaked to the public.
"I can't verify whether they are legitimate or not, what I can tell you is I'm very troubled by it," he said.
"We have an internal investigation occurring as we speak as to how those photographs were obtained by the public."
'I stayed in that exact same room'
When news emerged that Paddock had rained down bullets on a concert crowd in Las Vegas, Jeff Bridges realised he had been in that room before.
Mr Bridges and his partner were guests at the hotel in January last year, and they stayed in the same room where Paddock launched his attack — room 32-135.
During his stay, Mr Bridges filmed the room and the view from the windows, which included the concert venue — identical to the view Paddock had of the venue on Sunday evening.
Mr Bridges posted the video on social media in the aftermath of the shooting.
He described the room as "pretty spectacular" and panned the camera around the bathroom, sitting area and the view of Las Vegas from the window.
"I stayed in that exact same room last year," Mr Bridges said.
The video ends with a view down on the concert area.
Even the Las Vegas airport and the strip could be seen from the hotel room window.
Gunman transferred $100,000 overseas
Paddock, a high-stakes gambler and retired accountant, transferred $100,000 overseas in the days before the attack.
Investigators are taking a harder look at the shooter's girlfriend and what she might have known about the attack, as they try to determine why Paddock caused the massacre.
The ABC has been told Ms Danley left the Philippines on a flight to the United States late yesterday.
The Australian Federal Police has been assisting the FBI with inquiries into the woman who is a Filipino and Australian citizen. Las Vegas police say Ms Danley remains a person of interest.
They have been speaking with Ms Danley, who was out the country at the time of the shooting and in the Philippines.
Mr Lombardo said he was "absolutely" confident authorities would find out what set off Paddock.
Investigators are still trying to trace the $100,000 and are looking into at least a dozen reports over the past several weeks that said Paddock gambled more than $10,000 a day.
Mr Lombardo said the investigation was proceeding cautiously in case criminal charges were warranted against someone else.
Nevada's Gaming Control Board said it would pass along records compiled on Paddock and his girlfriend to investigators.