Lombardo previously said Campos was injured after the attack started, and, according to a police timeline, the first officers arrived on Paddock's floor at 10:17 p.m.
A small team of police officers, including two K-9 (sniffer dog squad) officers, a detective and a Special Weapons and Tactics (SWAT) team member, had swiftly converged on the Mandalay Bay Hotel and minutes later they breached into gunman's room on the 32nd floor.
The authorities now say that the security guard went to the 32nd floor of the hotel to investigate an alarm that went off in another room on the same floor, signaling that a door had been left open.
"We know that he attempted to shoot at the fuel tanks".
But Lombardo said he was flummoxed by the secrecy surrounding the madman's life and activities.
It took police an hour and 12 minutes from the first 911 call reporting the incident to locate Paddock.
Fasulo explained the change in the timeline by saying that dozens of investigators have been using different sources of information - including surveillance video, computers, police body cameras, cellphones and interviews - and that not all clocks are in sync.
Lombardo made the clarification at a news conference Monday about the ongoing investigation into the shooting and the possible motives for Paddock's October 1. killing spree.
Officials who are announcing a property return plan for concertgoers who fled gunfire at a Las Vegas music festival a week ago say more items will be made available in coming days for people who were in other areas of the venue.
"Mr Campos was encountered by the suspect prior to his shooting to the outside world".
Authorities now think the shooter checked into the suite on September 25, not the 28th as originally believed, though it was unclear if he occupied the room that early.
"A comprehensive picture is being drawn as to the suspect's mental state, and now, we do not believe that there is one particular event in the suspect's life for us to key on", Lombardo said.
Mr Lombardo declined to reveal what they have said, but added: "Every piece of information we get is one more piece of the puzzle".
Heal said that if police had known immediately that a guard had been shot, they would have rushed the room while the gunman was still firing. Tanner accompanied FBI's investigators as they have search warrant of Paddock's house.
"We are still speaking with Ms. Danley about the suspect's movements, gun purchases and anything else we need to know about him and how he had planned his assault, and who he came into contact with during the planning phase", Lombardo said.