"But what we have learned is that Mr. Campos was encountered by the suspect prior to his shooting to the outside world", Sheriff Lombardo said at a Monday news conference, his department's first update on the investigation in three days. Campos had been investigating an alarm that went off in another room on the same floor, signaling that a door had been left open.
Police said at the time that after injuring the guard, Paddock stopped firing into the crowd.
"Our officers got there as fast as they possibly could and they did what they were trained to do", Assistant Sheriff Todd Fasulo said. Paddock was gambling the night before, he confirmed, but police would not disclose the shooter's immediate actions before the crime.
Lombardo added that Paddock fired "well over 200 rounds" into the hallway when the security guard approached.
"He was able to confirm for us exactly what he heard in the moments before he was shot", Lombardo told reporters.
"The timeline associated with the original shot with Mr. Campos has changed through investigation", Lombardo said. "We believe he chose to take the lives he did and he had a very purposeful plan that he carried out". "But we want to work as hard and as focused as we can on it, and help the people that are in need for recovering from this, and heal together as a community".
Extensive research into the gunman's mental state found no occurrence in his life that may have triggered such a violent turn of events, police say.
There is still no evidence Paddock was motivated by ideology or that there was another shooter, he said.
"The sheer size of the space and the amount of personal items that were left there, it's just a huge undertaking", said Paul Flood, Unit Chief in the FBI Victim Services Division.
As investigators look at numerous different angles to find the motive behind the Las Vegas massacre, new details about the gunman have emerged.
"It's because this individual purposely hid his actions leading up to this event, and it is hard for us to find the answers to those actions", Lombardo said.
Still, Lombardo was clear that another prevailing question remains: Why did Paddock decide to carry out the attack in the first place?
The sheriff said, "We believe he chose to take the lives he did and he had a very purposeful plan he carried out".
Paddock was filmed driving along a road that leads only to an area that was used by locals to practice shooting, investigators discovered. Authorities do not yet know what made him stop shooting, Lombardo said.
According to Lombardo, Paddock had a document in the room with him, which contained numbers, but could not immediately say what they represented or what objective they served.