The mass murderer who gunned down 58 people during a Las Vegas music festival in October died of a self-inflicted gunshot to the mouth, a coroner’s report said.

Stephen Paddock’s death was ruled a suicide, according to Clark County, Nev., Coroner John Fudenberg.

Authorities said the high-stakes video poker gambler, 64, killed himself before officers reached his room.

All 58 deaths were ruled homicides in the deadliest mass shooting in modern U.S. history, authorities said. Twenty-one victims were shot in the head, 36 died with chest and back wounds and one died of a gunshot to a leg, the coroner's report said.

Four victims had multiple gunshot wounds.

The mass killer, armed with an arsenal of assault-style weapons and ammunition, also injured about 500 other people when he unleashed more than 1,100 rounds of gunfire from the 32nd floor of Mandalay Bay into a crowd of 22,000 people at the Route 91 Harvest Festival just below the hotel.

When police stormed Paddock’s suite after he stopped firing, they discovered shell casings all over the floor, the New York Post reported.

Authorities reported finding about 4,000 unused rounds along with the 23 guns in the suite.

However, authorities have not said why Paddock stopped shooting.

“My initial scan, coming in the room with my rifle, is just seeing, I’m seeing one male down, bleeding from the face,” Officer Matthew Donaldson told the Post. “He was not a threat. Kept going, kept going, kept going.”

Police and the FBI have also not said publicly what motivated him.

Autopsy reports in the case are not yet complete, officials said.

Paddock’s brain was sent to Stanford University in California to study after a visual inspection found no abnormalities.

The Associated Press contributed to this report.