It has been one year since the Las Vegas shooting rocked the US. Here's exactly how the nation's worst modern gun massacre unfolded

Paddock first arrived at the Mandalay Bay almost a whole week before the shooting.

Police originally said he checked in on Thursday September 28, but later updated the date to Monday 25, three days before.

According to the Associated Press, he asked for a high-level suite overlooking the Route 91 Harvest festival — but couldn't immediately get one.

A hotel source said that he didn't move in to the 32nd-floor room he used for the shooting until Saturday, the night before the attack.

The AP said he "was given the room for free because he was a good customer."

The Las Vegas Metropolitan Police Department (LVMPD) say they found 23 guns and thousands of rounds of ammunition in his room.

He appears to have planned meticulously for the attack. As well as a large number of guns, Paddock set up at least three cameras to monitor the corridor outside, police said.

According to Fox News, the country star Jason Aldean went onstage at 9:40 p.m. on the night of the shooting. He played for half an hour before the shooting began.

Las Vegas radio station 95.5 The Bull shared the line-up on Twitter before the event.

Aldean escaped unharmed and later paid tribute to his fans who were hurt and killed.

The shooting began with a hail of bullets on the crowd below, fired from Paddock's hotel room.

Using multiple rifles, Paddock opened fired on the crowd of 22,000 people below him, from a distance where he would have had no ability to distinguish individual targets.

Officers started to exchange radio messages about the shooting.

Las Vegas police say that Paddock fired "a dozen or so volleys" overall during the shooting.

Watch footage from the scene here.

(NB: Earlier versions of the police timeline said the shooting began at 9:59 p.m. They have been revised.)

Citing police radio transmissions, The New York Times said officers around Route 91 Harvest were still working out what was happening while colleagues inside the hotel were closing in.

Here two lines time-stamped 10:13 p.m.:

"It's coming from like the 50th or 60th floor, north of the Mandalay Bay! It's coming out a window.

"We're seeing local flashes in the middle of Mandalay Bay on the north side, kind of on the west tower but towards the center of the casino, like one of the middle floors."

One of the earliest records of the shooting is a tweet from the user @GLOKMIN.

"i'm pretty sure a terrorist attack just happened next to me im at mandalay bay," they wrote.

Again citing police radio, The New York Times said officers were right outside Paddock's hotel room at 10:24 p.m., 19 minutes after the shooting began.

One message said: "I'm on the 32nd floor. The room is going to be 135."

Another said: "It's room 135 on the 32nd floor. I need the SWAT."

It would be almost another hour, however, until officers would break into Paddock's room.

Taxi drivers in the area received a message direct from the police at 10:25 p.m. telling them to avoid the Mandalay Bay area.

According to Reuters, it said: "Drivers avoid LV Blvd and Tropicana. Active shooting from Mandalay Bay. Possible 3 shooters."

Almost 40 minutes after the attack began, the Las Vegas Metropolitan Police Department wrote on Twitter that it was investigating an ongoing shooting.

According to Newsweek, officers asked permission to enter Paddock's room sooner but were told to wait for SWAT teams.

Las Vegas Metropolitan Police Department Undersheriff Kevin C. McMahill defended that decision in a press conference.

He said officers were right to wait because Paddock was "contained" and had stopped firing out of the window.

He said: "The floor had been evacuated of any guests, the suspect was contained and isolated within a room."

One hour and five minutes after the first shots were fired, a police SWAT unit detonated an explosive device to break down Paddock's door, according to the police timeline.

By this time Paddock had already killed himself.

"The Strike Team reported Paddock was down from an apparent self-inflicted gunshot wound to the head," the final report said.

SWAT officers noticed a second, closed, door when they burst into Paddock's suite, and could not immediately be sure what was behind it.

They used a second explosive charge to burst it open, at which point they could see the entire suite and were certain that Paddock had been alone.

Two minutes before midnight, and almost two hours after the first shots were fired, the Las Vegas police tweeted confirmation that "one suspect is down".

It was not until 31 minutes past midnight — more than an hour since Paddock was found dead — that the police department sent a follow-up tweet saying it thought the dead man was the only attacker.

Two hours, 26 minutes after it began, the massacre was officially over.

The final death toll was 58. More than 800 people were injured.

Police concluded their investigation ten months after the shooting, and said they could not determine the motivation behind it.

Paddock did not leave a suicide note, the investigation concluded. There was no evidence he belonged to any terrorist organizations or hate groups, and he did not have a criminal record.

Police determined that he acted alone.

Investigators followed 2,000 leads, watched 22,000 hours of video, and examined 252,000 images.