Sheriff Lombardo said there was evidence to suggest the 64-year-old retired gambler intended to stay alive after he killed 59 people and injured more than 500 from his 32nd floor room at the Mandalay Bay Hotel and Casino on Sunday night.
But the sheriff did not say what the evidence was.
The disclosures were among several new details revealed by the clark county sheriff, who also speculated Paddock could have “had help”.
LAS VEGAS SHOOTING
“You’ve got to make the assumption he had to have some help at some point.”
This was after initially describing Paddock’s killing spree as a “solo act”.
It comes as it emerged Paddock had rented a room at the Ogden luxury apartment complex through Airbnb, overlooking the Life is Beautiful festival in Las Vegas, which took place a week before the Route 91 Harvest Festival.
Sheriff Lombardo said: “Was he doing pre-surveillance? We don’t know yet.”
He said Paddock could have been a “a super guy” who was “working out all of this on his own”, but added: “It would be hard for me to believe that.”
It comes after Paddock’s girlfriend Marilou Danley, 62, returned to the US from a trip to the Philippines on Wednesday to be questioned by FBI chiefs.
She had allegedly been “sent away” by Paddock so she could not get in the way of his deadly massacre.
Investigators declared the Australian national a “person of interest” in connection with the killing and believe she could be key to understanding what led retired accountant Paddock to carry out the deadliest mass shooting in US history.