Investigators trying to determine what sparked the Las Vegas mass shooting carried out by gunman Stephen Paddock have said the massacre which claimed 58 lives was meticulously planned with the means and desire to inflict unprecedented carnage.
Before he mowed down concert goers from his 32nd floor suite at the Mandalay Bay Hotel here on Sunday night, Paddock created a ring of surveillance around him, law enforcement officials said on Tuesday.
Video cameras in his suite, two cameras in the hallway and one in the suite door peephole allowed Paddock to see if law enforcement or security were approaching. But investigators were still at a loss to establish a motive for the massacre, the New York Times reported.
Police also found 23 guns, hundreds of rounds of ammunition, and other equipment in the gunman's hotel suite. Several firearms and explosives were retrieved at his home. In total, across three locations, 47 firearms were recovered.
The authorities revised the death toll down from 59 on Tuesday evening, saying that one of the bodies was that of the gunman.
Paddock's girlfriend Marilou Danley, who had been in the Philippines, returned to Los Angeles on Tuesday evening. She was accompanied by Federal Bureau of Investigation agents and was to be questioned by the Las Vegas police.
In the immediate aftermath of the shooting, police had described Danley as a "travelling companion" of the shooter, but did not describe her as a suspect.
Clark County Sheriff Joseph Lombardo said she might shed some light on what was going through the mind of the gunman, who killed himself as the police prepared to enter his room.
"This individual was pre-meditated... the fact that he had the type of weaponry and the amount of weaponry in that room.
"... He evaluated everything he did in his actions," Lombardo said.
Twelve of the rifles Paddock had were outfitted with a "bump stock", a device that enables a gun to fire hundreds of rounds per minute like a machine gun officials said.
Paddock checked in last Thursday and kept the "Do Not Disturb" sign on his door for the next three days, said a hotel worker.
The shooting -- the worst in modern US history -- sparked debate over US gun laws, but President Donald Trump said the discussion over what, if anything, needs to be done was "not for now".
With hundreds of victims still hospitalised, officials said the death toll was likely to rise.