Photographs leaked Tuesday from the hotel room of the Las Vegas shooter showed scope-mounted assault rifles, a floor covered with expended shells and what appears to be a note left on a table.
Las Vegas Sheriff Joseph Lombardo said that Stephen Paddock, the man who murdered 59 people from the 32nd floor of the Mandalay Bay Hotel, also had cameras in his room, including one apparently monitoring the corridor approach.
Lombardo said his department was investigating the photographs from inside and outside the room published by Boston 25 TV station and Germany's Bild magazine.
One showed the apparent body of the shooter next to two assault rifles mounted on bipods, his feet next to a table with an apparent hand-written note on it.
Other pictures from the scene show a neatly stacked pile of ammunition clips, and other rifles piled up on lounge chairs.
A picture outside the room shows bullet holes through the door, possibly those made when Paddock fired at hotel security guards outside the door, hitting one in the leg.
Lombardo said Paddock shot from the hotel window down at the crowd of about 22,000 at a country music concert late Sunday for about nine minutes in total.
Fifty-nine people have been confirmed dead in the massacre and about 500 were treated in hospitals for a range of wounds and injuries.
Lombardo said there was still nothing clear about the motivation of the shooter, a 64-year-old regular gambler who owned numerous properties and had no known associations with political, radical or hate groups.
He did not comment on the content of the pictures, but confirmed Paddock had used a "bump stock" on at least one of the weapons, which in effect turned it into an automatic rifle that can shoot hundreds of rounds a minute.
Outside the room investigators found one of the cameras mounted on a room service cart in the hallway, possibly giving Paddock a view of anyone approaching the room.
"I'm not aware of any transmission. But there were cameras," Lombardo said.