UPDATE [10/2/17 – 12:30 PM EDT]:

This morning, the world awoke to the the horrifying news of a deadly mass shooting during a music festival on the Las Vegas strip that claimed the lives of more than 50 people and saw 400+ more people injured, as thousands more looked on in terror. According to reports, a lone gunman opened fire into the crowd attending the open-air country music concert, Route 91 Harvest Festival at the Las Vegas Village from a 32nd floor window of the adjacent Mandalay Bay Resort and Casino beginning during country singer Jason Aldean‘s performance. The death and injury tolls make this one of the deadliest mass shootings in United States history.

The gunman has been identified as 64-year old Stephen Paddock of Mesquite, NV. Police responded to reports of the shooting just after 10 p.m. (1 a.m. ET), and the suspect was apprehended and fatally shot in the Mandalay Bay Resort and Casino, officials said. The sheriff also said authorities think they have found Marilou Danley, the woman believed to be traveling with the suspect.

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.

NBC News spoke to people who were at the concert when the shooting occurred. “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,” Meghan Kearney described to 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.”

“After the second round… everybody hit the ground around us,” concert-goer Sean said on TODAY. “It seemed like people were hit everywhere.”

Aldean later said via Instagram that he and his band were safe. Witnesses said that the first round of shots sounded like fireworks. Only after the second burst of gunfire did the band stop playing. Another concergoer, Jon Bessette, described a scene of “pandemonium” as “the band ran off stage. Everyone was running, people were getting trampled,” he said.

You can view a shot of the large crowds attending the festival on the highly trafficked Las Vegas Strip from the first day of Route 91 Harvest Festival below, via the festival’s Facebook page. The event organizers have yet to officially comment on the horrifying events of Sunday evening.

Police have urged families looking to locate missing loved ones to call 1-866-535-5654.

This story is developing. Check back for updated on last night’s horrific events in Las Vegas. Our thoughts and prayers go out to anyone and everyone affected by this senseless act of violence.

[Cover photo via David Becker/Getty Images/NYT]

[via NBC News]