At least 58 people have been killed and 515 injured in a mass shooting at a Jason Aldean concert at a festival outside the Mandalay Bay Hotel and Casino in Las Vegas. It's the most deadly mass shooting in U.S. history and the most deadly terror attack since 9/11.

https://www.instagram.com/p/BZvRZnogBrI/?hl=en&taken-by=jasonaldean

The gunman was shooting at a crowd assembled at the concert from the 32nd floor of the hotel. He has been identified as 64-year-old Jason Paddock of Mesquite, Nevada.

First photo released of the Las Vegas shooter, 64-year-old Stephen Paddock; he was found dead in Mandalay Bay hotel room he fired shots from pic.twitter.com/hr6O5UApHf

— Good Morning America (@GMA) October 2, 2017

The gunman, who had at least 10 rifles in his room, took his own life, according to police.

"There were people bleeding everywhere. One man next to me had a bullet hole through his arm," Las Vegas shooting eyewitness on @TODAYshow pic.twitter.com/mS3lq0pWde

— NBC News (@NBCNews) October 2, 2017

Videos on social media show people ducking and then fleeing the automatic gunfire.

https://twitter.com/LukeBroadlick/status/914757815926792192?ref_src=twsrc%5Etfw&ref_url=https%3A%2F%2Fwww.mediaite.com%2Ftv%2Fat-least-20-dead-in-mass-shooting-at-las-vegas-music-festival%2F

New video of gunfire and panic during #route91harvest #LasVegasShooting just into @News3LV pic.twitter.com/YkLb7qPWD2

— Victor Hernandez (@ToTheVictor) October 2, 2017

People duck for cover at the sound of gunfire in Las Vegas. At least 20 have died in a shooting on Sunday night https://t.co/N9l2h2BdRt pic.twitter.com/bXVeX1WFxu

— CNN (@CNN) October 2, 2017

NBC reports:

Police responded to reports of the shooting just after 10 p.m. (1 a.m. ET), and the suspect was fatally shot in the Mandalay Bay Resort and Casino, officials said.

Authorities found several weapons in Paddock's room after using explosives to enter, law enforcement officials reported. It was not immediately clear what kinds of weapons were found.

At least one off-duty Las Vegas police officer was shot, Lombardo said. Several other off-duty police officers are believed to be among the dead and injured.

Meghan Kearney described the chaotic scene.

“We heard what sounded like firecrackers going off. Then all of a sudden we heard what sounded like a machine gun. People started screaming that they were hit… When we started running out there were probably a couple hundred [people] on the ground,” she told MSNBC.

“People kept dropping and dropping. … People were getting shot one foot away from us,” she said. “People were trying to save their friends. There were gunshots everywhere. Helping them would've meant that we got shot, too.”

Police have located Paddock's roommate, Marilou Danley, 62, Lombardo said. They also found two vehicles related to the investigation: a Hyundai Tuscon and a Chrysler Pacifica Touring, both with Nevada license plates.

Trump tweeted about the attack:

My warmest condolences and sympathies to the victims and families of the terrible Las Vegas shooting. God bless you!

— Donald J. Trump (@realDonaldTrump) October 2, 2017