Stephen Paddock may have been planning to escape after carrying out America's deadliest gun massacre.
The 64-year-old shot himself before police got to him - but it is thought he may have initially planned to make a getaway with 1,600 rounds of ammunition in his car.
Police were still working to determine whether the killer worked alone or had some kind of assistance.
Revealing more details about the case, Sheriff Joe Lombardo said Paddock fired on crowds attending the Route 91 Harvest Festival for a full 10 minutes.
When he checked into the Mandalay Hotel on October 1 he specifically requested a high-rise room.
It also emerged Paddock had rented rooms overlooking other music festivals in the run up to Sunday night's attack.
Just a week before, the retired accountant checked into a hotel near the Life Is Beautiful festival, where British band Muse were playing.
And in August, Paddock rented a similar room overlooking festival-goers at Lollapalooza in Chicago.
Paddock's girlfriend Marilou Danley, who was out of the country at the time of the attack, said she had no idea what he was planning.
The 62-year-old said she feared Paddock was breaking up with her after he wired her money to buy a house - having paid for a cheap ticket for her to visit family in the Philippines a few weeks ago.
"It never occurred to me in any way whatsoever that he was planning violence against anyone," she said in a statement after flying back to the US to help investigators.
Ms Danley said she was "devastated by the deaths and injuries" saying: "I am a mother, and a grandmother, and my heart breaks for all who have lost loved ones."
She said: "I knew Stephen Paddock as a kind, caring quiet man. I loved him and hoped for a quiet future together with him.
"He never said anything to me or took any action that I was aware of that I understood in any way to be a warning that something horrible like this was going to happen."
Ms Danley has not been charged in the case but is being classed as a person of interest.
According to immigration documents, she had flown to the Philippines on September 15, left on September 22 then returned three days later on a flight from Hong Kong. She was travelling on an Australian passport.
Ms Danley's Australia-based sisters believe Paddock sent her away to prevent her from interfering with his plans.
In an interview with Australia's Channel 7 TV network they said she was a "good person" who was "traumatised" by what had happened.
"I know that she doesn't know anything as well, like us," one of them said.
Ms Danley's statement came as police revealed a detailed timeline of Sunday night's attack.
The first shots were fired at 10.05pm and ended a full 10 minutes later at 10.15pm.
But police did not get into Paddock room's for another hour later.
On entering the 32nd floor suite, they found him dead surrounded by an arsenal of weaponry.
The investigation continued as US President Donald Trump praised the bravery of the concert goers who helped the injured along with the first responders.
"I just have to tell you I just met some of the most amazing people," he said after flying in to Las Vegas.
"The bravery, some were very, very badly wounded. And they were badly wounded because they refused to leave, they wanted to help others.
"Some let others go in ambulances before them because they were more badly injured. It's incredible."