"We have uncovered no evidence to show there was a second shooter", Lombardo told reporters. But the guard managed to direct police to the exact location of Paddock's suite and even provided a hotel key to officers looking to clear rooms on the 32nd floor before they insisted he get medical attention.
This revelation raises the question of what caused Paddock to stop the attack, as previously it was thought to be the interruption of the security guard.
The sheriff said he had gleaned insight from the trip to Mumbai and his department now reacts faster to such shootings, quickly forming a team to "cease the action" of the assailant on their own.
The US investigators continue to make efforts to find out the motive of the shooter who showered bullets from a semi-automatic rifle from a hotel window overlooking the site of a music festival in Las Vegas on Sunday.
Police say they remain in contact with Paddock's brother, along with other family members, and his girlfriend, Marilou Danley, regarding discussions about the gunman's behavior.
"It's amazing" that Campos didn't sustain more injuries, Lombardo said.
Paddock's final shots were fired at 10:15 pm. Police found Paddock dead of an apparent self-inflicted gunshot upon entering his suite.
Lombardo acknowledged that "we do not know why at this point" why that gunfire ended - but he cast the revision as one of a number of "minute changes" common to an evolving investigation.
They said a piece of paper found in the shooter's hotel room had calculations scrawled across it determining ballistic trajectories that would help the gunman maximise his death toll.
Sheriff Lombardo also said police are confident that Paddock carried out the massacre alone.
"He actually cared about everybody", Lisa Crawford, who worked for Paddock managing an apartment he owned from 2006 to 2012, said.
Crawford said she had an emotional breakdown after the massacre, adding that she feels "guilty" for having known Paddock.