Police on Monday said that Stephen Paddock shot a hotel security guard six minutes before he began shooting concertgoers from his hotel room at the Mandalay Bay Resort and Casino - a striking change from an earlier police timeline of events.
"He was injured prior to the mass volume shooting", Lombardo told reporters, announcing a new timeline to the shooting.
Paddock arrived at the Mandalay Bay on September 28, three days before the concert shooting, bringing with him 23 guns, a dozen of them equipped with "bump stocks, " which allow for more rapid fire.
However, the authorities do not know what made him stop shooting, as yet, the CNN reported.
It was not immediately clear why the timeline of the shooting changed a week later and what its effect could be on the investigation.
The ajar door was not Paddock's, but the sheriff had said it was a lucky coincidence that put the security guard at the shooter's location.
"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.
Far from the Las Vegas Strip and its flashy hotels, a small healing park opened Friday in the north of Las Vegas, as communities shaken by Sunday's horrific mass shooting join together to grieve.
Police said Paddock managed to fire off over 200 rounds as the security guard approached the suspect's room alone.More news: Astros soundly beat Red Sox in ALDS Game 1
Assistant Clark County Sheriff Todd Fasulo told The Associated Press that police got to Paddock's room as fast as they could and that not all clocks are in sync with each other, perhaps accounting for some of the conflicting reports.
"He's like on retainer, I call it, I guess", Paddock said of the doctor.
More than a week after a gunman opened fire on a concert in Las Vegas, killing 58 people and leaving hundreds of others injured, authorities say those chaotic minutes are still coming into focus.
Lombardo's announcement also raises the question about why Paddock stopped firing during his rampage.
A note containing handwritten numbers for wind, trajectory and distance was discovered by Stephen Paddock's body inside the Mandalay Bay room.
Lombardo said that he believed Paddock was planning an escape route and was going to shoot at fuel tanks below to cause a distraction. It is believed the shooter was drilling to place a camera or a rifle in position in the suite, the sheriff said.
"As I've said from Day 1, we want to figure out the "why" to this, and we'd like to know the motive", Lombardo said.
"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.