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.

FILE - In this Oct. 3, 2017, file photo, windows are broken at the Mandalay Bay resort and casino in Las Vegas. Authorities said Stephen Craig Paddock broke the windows and began firing with a cache of weapons, killing dozens and injuring hundreds. Attorneys for a California woman wounded in the Oct. 1 mass shooting that killed 58 and left hundreds injured on the Las Vegas Strip have dropped a gun accessories maker from her negligence and damages lawsuit. One of Rachel Sheppard's lawyers, Craig Eiland, said Thursday, Dec. 7, 2017,  the decision to strip Slide Fire Solutions from the case lets him focus claims against hotel owner MGM Resorts International and concert promoter Live Nation Entertainment. (AP Photo/John Locher, File)

Stephen Paddock fired from the 32nd floor of the Mandalay Bay Hotel and Casino, Oct. 1, 2017.

 (Associated Press)

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.

Varias cortinas salen de unas ventanas rotas en el hotel y casino Mandalay Bay en Las Vegas, el lunes 2 de octubre de 2017. Las autoridades dijeron que el atacante Stephen Craig Paddock rompió las ventanas y comenzó abrir fuego, donde mató a decenas de personas e hirió a centenas. (AP Foto/John Locher)

Broken windows mark gunman Stephen Paddock’s hotel suite in Las Vegas.

 (Associated Press)

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.