A lone gunman shooting from a hotel room in Las Vegas' Mandalay Bay killed more than 50 concert-goers and injured more than 400 Sunday night (October 1) in what has since been deemed the deadliest domestic attack in modern United States history.

According to The New York Timesa crowd of thousands at Route 91 Harvest Festival, a three-day country music event, was sent into panic sometime after 10 PM, when the gunman opened fire onto the crowds while Jason Aldean performed. Police said the suspect was dead when they found him in his rotel room, but say there was "a companion" that they are "confident" they've found.

The suspect was said to have upwards of 10 rifles at his disposal.

Aldean wrote in an Instagram post that the night was nothing short of a nightmare.

“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,” he noted.

Witnesses told the Times that the gunfire was seemingly endless.

“It just kept coming,” Robyn Webb told The Las Vegas Review-Journal. “It was relentless.”

The Harvest Festival, which was playing out its final night, was sold out, and drew close to 40,000 attendees.

Close to 16 months ago, a shooting at Orlando's Pulse club left 49 people dead — then, it was the deadliest domestic attack in United States history. And the Las Vegas shooting comes just four months after a deadly attack at Ariana Grande's concert in Manchester, England, in which a bomber killed more than 20 and injured dozens as the show ended and patrons began to leave the venue.

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