The gunman who attacked a Las Vegas country music festival installed cameras outside his hotel room, including at least one in a room service cart, to watch for the approach of police officers, Clark County Sheriff Joe Lombardo said Tuesday.

Officials still haven't offered a motive for why Stephen Paddock, 64, of Mesquite, Nev., opened fire at a concert across the street from the Mandalay Bay Resort and Casino on Sunday night. Fifty-nine people were killed and more than 500 injured in the attack.

But Lombardo said additional information obtained by investigators revealed the extent to which Paddock apparently "pre-planned extensively" for the attack, reports the Los Angeles Times.

One Mandalay Bay security guard, who had become separated from police, was shot in the leg through the door of Paddock's room when he approached, Lombardo said. The security guard escaped and police surrounded the room, eventually breaking inside, where they discovered that Paddock had killed himself.