More than 50 people were killed and over 200 injured when a "lone wolf" gunman opened fire on people attending a country music festival in Las Vegas, police said.

It is the most deadly mass shooting in modern U.S. history.

Authorities shut down part of the Las Vegas Strip and Interstate 15 after receiving reports of an active shooter at the Route 91 Harvest festival, near the Mandalay Bay Casino at about 10:10 p.m. local time.

Authorities ruled out terrorism, NPR reported.

The White House said President Trump has been briefed.

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

At least 50 dead, more than 200 injured in Las Vegas shooting

Lombardo said police were confident that they had located a person of interest who he named as Marilou Danley, the suspect's roommate. He described her as an Asian female, about 4 foot 11 inches tall and weighing 111 pounds

He said officers also located a Hyundai Tucson and a Chrysler Pacifica Touring, both with Nevada plates, which were registered to the dead suspect.

Sheriff Joe Lombardo of Las Vegas Police confirmed at a news conference that the shooter had fired from the 32nd floor of the Mandalay Bay. He said officers responded and the suspect was dead. Numerous firearms were found in the room at the scene.

He named the suspect as Stephen Paddock, 64, a local resident.

Lombardo said reports of multiple shooters and explosives were false. Some of the deceased were police officers, he added.

Videos on social media show people ducking for cover and fleeing as gunfire rings out.

Ivetta Saldana, who was attending the festival, told The Las Vegas Review-Journal she hid in a sewer after the shooting began.

“It was was a horror show,” she told the newspaper. “People were standing around, then they hit the floor.”

Witnesses said they saw multiple victims and dozens of ambulances. Some concert-goers huddled in the basement of the nearby Tropicana hotel-casino.

Nevada Gov. Brian Sandoval tweeted: "A tragic & heinous act of violence has shaken the #Nevada family. Our prayers are w/ the victims & all affected by this act of cowardice."

Some flights destined for the McCarran International Airport were diverted due to the incident.

The three-day Route 91 Harvest festival started Friday and is reported to have attracted 30,000 attendees. The shooting occurred on the final night, during a performance by Jason Aldean. Aldean confirmed that he and the rest of his team were safe.

"Tonight has been beyond horrific," Aldean posted on Instagram. "I still dont (sic) know what to say but wanted to let everyone know that Me and my Crew are safe. 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."