Nearly 60 people are dead, with more than 500 injured, after a mass shooting last night during a country music festival in Las Vegas.

Local police said a gunman opened fire on the Route 91 Harvest Festival from the 32nd floor of the nearby Mandalay Bay hotel during a performance by Jason Aldean at approximately 10:08 PM local time, according to CNN.

The rising death toll has already surpassed that of a 2016 massacre at the Pulse night club in Orlando, making the Las Vegas tragedy the deadliest mass shooting in modern American history, the Washington Post noted.

Sheriff Joseph Lombardo said that the assailant was later "engaged" by authorities, but killed himself as a SWAT team burst into the hotel room where he had been firing down at concertgoers, the Los Angeles Times reported.

Police later identified the shooter as 64-year-old Stephen Paddock, of Mesquite, Nevada. Lombardo said Paddock was acting alone: "Right now, we believe it's a sole actor – a lone wolf-type actor." Authorities have since located a roommate identified as Marilou Danley who was believed to be with Paddock. She was initially said to be a person of interest in the shootings, but was later cleared.

The shots arrived so rapidly that at first concertgoers thought they were pyrotechnics. “We heard what sounded like firecrackers going off,” attendee Meghan Kearney told MSNBC. “Then all of a sudden we heard what sounded like a machine gun. People started screaming that they were hit. … Then we started running out. There were probably a couple hundred [people] on the ground.”

At one point, authorities shut down a portion of the Las Vegas Strip and Interstate 15 as the active-shooter reports spread, USA Today reported. A spokeswoman said University Medical Center was treating "many patients" with gunshot wounds, according to the Times. First responders were so overwhelmed that concertgoers were arriving overnight with victims loaded into personal vehicles.

Aldean was not injured in the shooting. “Tonight has been beyond horrific. I still don’t know what to say but wanted to let everyone know that me and my crew are safe,” the country singer wrote on Instagram.

Omar Mateen, who professed allegiance to the Islamic State, killed 49 people in June 2016 at Orlando. Before that, the record death toll for an American mass shooting was 32, dating back to 2007 at Virginia Tech.

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