Police have made a significant change to the timeline of the Las Vegas mass shooting, saying the gunman shot a hotel security guard before he opened fire on concert-goers.
Clark County Sheriff Joe Lombardo had previously said the guard was shot after Stephen Paddock fired at the country music festival and that the guard's arrival in the hallway of the Mandalay Bay hotel may have caused him to stop firing.
Mr Lombardo said security guard Jesus Campos was in a hallway of the Mandalay Bay hotel responding to a report of an open door when he heard drilling from Paddock's room.
Paddock, who had installed three cameras to monitor the approach to his suite, opened fire through the door, spraying 200 shots down the hall and wounding the guard, who alerted other security officials.
A few minutes later, Paddock began raining down bullets for 10 minutes in an attack that killed 58 people - the deadliest mass shooting in modern US history, Mr Lombardo said.
Authorities also said Paddock targeted aviation fuel tanks, stocked his car with explosives and had personal protection gear as part of an escape plan.
He had power tools and was attempting to drill a hole in an adjacent wall, perhaps to mount another camera or to point a rifle through, but he never completed the work, Mr Lombardo said.
He also drilled holes and bolted a metal bar to try to prevent the opening of an emergency exit stairwell door near the door of his room.
Mr Lombardo again expressed frustration with the pace of the investigation, but not with the investigators who have yet to pinpoint the motive behind Paddock's decision to fire from the 32nd floor of the Mandalay Bay hotel casino on a Las Vegas Strip concert crowd of 22,000 on October 1.
"It's because this individual purposely hid his actions leading up to this event, and it is difficult for us to find the answers to those actions," Mr Lombardo said.
"We believe he decided to take the lives he did and he had a very purposeful plan that he carried out."
There is still no evidence Paddock was motivated by ideology, or that there was another gunman, he said. Investigators have found 200 incidents of Paddock moving through the city, and at no time was he with anyone else.
Mr Lombardo said police and FBI agents, including behavioural profilers, have still not found a particular event in Paddock's life that might have triggered the shooting.
The sheriff added that a complete evaluation of Paddock's mental condition was not yet done. Authorities did not find a note in his room, only a paper with numbers, he said.
Investigators believe the numbers represented calculations for more precise shots, according to a law enforcement source.
The sheriff also confirmed investigators are talking with Paddock's brother Eric, who travelled to Las Vegas, and continue to speak with the gunman's girlfriend Marilou Danley.
Mr Lombardo declined to reveal what they have said, but added: "Every piece of information we get is one more piece of the puzzle."