When retiree Stephen Paddock checked into his room at the Mandalay Bay hotel last Thursday, it was just one of the many rooms he had asked for as a courtesy. He was a skilled video poker gambler who was known to be spending at least $20,000 a night in the casino. He was given a large suite that had uninterrupted views of the Las Vegas Strip, and a clear view of the Route 91 Harvest festival music event across the street, which would have been about 400 yards away from his room.

On Sunday evening, at the end of the final performance by Jason Aldean, Paddock opened fire with an arsenal of assault-style rifles from his 32nd floor hotel room, killing 58 and wounding hundreds. The massacre was the deadliest mass shooting in modern United States history.

Police said that the gunman, 64-year-old Stephen Paddock of Mesquite, Nevada, had been at the venue for about an hour and was dressed in a dark suit. He opened fire with an assault-style rifle and an AR-15, which he had legally purchased.

He had a “bump stock” device and high-capacity magazines for his guns. He also had bipod braces and scopes.

After he had armed himself, Paddock opened the door to his hotel room and began firing at the festival crowd below. He used multiple rifles and fired a total of about 1,000 rounds, according to Las Vegas Metropolitan Police Department Sheriff Joseph Lombardo.

As he began his shooting, Paddock aimed for the heads of his victims. He was able to do this because his hotel room had two windows, allowing him to shoot from a range of about 200 feet.

During the gunman’s rampage, police recorded a series of radio messages from the room above him. They were transmitted to police officers on the ground, who began to search the floor from above. At one point, officers were able to find an injured security guard and tell him the room number that was the shooter’s, according to a timeline released by the LVMPD on Tuesday.

The first police arrived on the scene 19 minutes after the shooting began, but it took about an hour to enter the room and begin searching for the shooter. By 10:24 p.m., two police officers were in the room. They then found Campos, the security guard who had been shot, and he told them the room number was Paddock’s.

In the room, police say they found 23 guns and thousands of rounds of ammunition. They also said that Paddock had set up at least three cameras to monitor the hallway outside his hotel room.

Paddock was a prolific gambler who had won millions of dollars, and he was also a longtime resident of the city. He had a stable relationship with his girlfriend, and he was financially stable. He also did not have any apparent grudges against the United States, he did not have any serious health problems and was in good mental condition. He reportedly had no history of violence and was never arrested before the shooting.