At least 58 people have been killed in America’s deadliest mass shooting after a single gunman positioned on the 32nd floor of a Las Vegas hotel opened fire on a crowd of 22,000 music fans attending a country-music festival shortly after 10 p.m. Sunday night local time.

The late-night murder spree is now the deadliest mass shooting in U.S. history, surpassing the death toll of Orlando’s Pulse nightclub massacre, which killed 49 people in 2016.

More than 500 people were taken to local hospitals, Clark County Sheriff Joe Lombardo said Monday morning.

The suspected shooter, a man who lived locally, was identified as 64-year-old Stephen Craig Paddock.

He had an arsenal of at least 10 rifles in the hotel room from which he launched his attack, police said in a briefing before sunrise.

According to Deputy Sheriff Kevin McMahill, Paddock shot himself as police made entry to the hotel room he had occupied.

Paddock, who lived in a retirement community, had occupied the hotel room since Sept. 28.

Police also said they had cleared of any involvement a woman earlier named as a person of interest. A spokesman said they had located Marilou Danley “out of the country,” adding, “We have had a conversation with her and we believe her at this time not to have been involved.”

She and Paddock had the same address. According to LinkedIn, Danley worked as a “Gambling & Casinos Professional” in Reno, Nevada.

Meanwhile, witnesses have been posting footage on social media of the horrific scenes that unfolded at Route 91 Harvest, a festival that was taking place across the street from the Mandalay Bay Resort and Casino.

Country star Jason Aldean was performing one of the festival’s final sets when automatic gunfire broke out.

Immediately after the shooting started, the band was rushed off the stage.

Aldean later said: “My thoughts and prayers go out to everyone involved tonight. It hurts my heart that this would happen to anyone who was just coming out to enjoy what should have been a fun night.”

“People went down on the Mandalay side of the stage,” one concertgoer, Joe Pitzel, told CNN. “I don’t know if people were ducking or if people were hit.”

Eyewitness Bryan Heifner spoke to CNN from a room in a hotel across from Mandalay Bay, which he said he could see from his window.

“Mostly I heard the shots, just so many shots—I just thought it was a semi braking with the air brakes, but then I went downstairs and saw people running and looking for family,” he said.

“I immediately went back to my room, locked the door, turned the lights off.”

A concertgoer told CNN affiliate KLAS: “Everybody’s hiding everywhere, they’re hiding under the bleachers and the stanchions, anywhere they could and everyone is telling us to ‘Run. Run as fast as you can.’”

Concertgoers reported seeing muzzle flashes from the upper floors of the Mandalay Bay hotel and casino across Las Vegas Boulevard.

Within minutes of the attack, witnesses posted video footage on social media of gunfire, and artists at the festival tweeted about hearing gunshots.

Las Vegas City Hall said it was a “very sad night for Las Vegas” and warned members of the public to stay away from the south end of the Vegas Strip, where Mandalay Bay is located.

In a statement, police said “among the dead is an LVMPD officer who was off-duty at the time. His name is being withheld pending notification of next of kin. There were also two on-duty officers injured, one of whom was upgraded recently from critical to stable condition. The other sustained non-life threatening wounds.”

Police asked those wishing to help to donate blood. United Blood Services will start taking donations at 7 a.m. at two locations: 6930 W. Charleston in Las Vegas or 601 Whitney Ranch Drive in Henderson.

UMC will also be hosting a blood drive in conjunction with United Blood Services. It will be held at UMC’s Delta Point Building located at 901 N. Rancho Lane.