Stephen Paddock, the gunman who killed 59 people and injured more than 500 in Las Vegas on Sunday, set up a number of cameras in and around his hotel suite.
Clark County Sheriff Joseph Lombardo said the cameras, including one on a service cart, appeared to be in place to monitor the police.
Police are still trying to determine why Paddock, 64, opened fire on a concert from the Mandalay Bay Hotel.
However, they do know there was a high degree of planning.
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Sheriff Lombardo told reporters on Tuesday: “This individual was pre-meditated. Obviously pre-meditated, the fact that he had the type of weaponry and the amount of weaponry in that room.
“It was pre-planned extensively and I’m pretty sure he evaluated everything he did in his actions.”
The shooting – the worst in modern US history – has sparked debate over US gun laws, but President Donald Trump has said the discussion over what, if anything, needs to be done was “not for now”.