PHOTO: People carry a an injured person at the Route 91 Harvest country music festival PHOTO CREDIT: ABC NEWS

At least, 20 people have been confirmed dead while over 100 were injured after a gunman opened fire on concertgoers at a country music concert on the Las Vegas Strip Sunday night, police said.

Associated Press quoted witnesses as saying that they could see muzzle flashes coming from the Mandalay Bay Hotel and Casino’s high floors accompanied by the sound of automatic gunfire.

Police confronted the gunman on the hotel’s 32nd floor who was identified as a local resident .

Washington Post reports that the shooting appeared to take place near the Route 91 Harvest Festival, a three-day country music concert held over the weekend that reportedly drew 30,000 attendees. The concert grounds are adjacent to Mandalay Bay.

One witness, Ivetta Saldana, told the Las Vegas Review-Journal that Aldean was rushed off stage when the shots rang out. “It was a horror show,” she said. “People were standing around, then they hit the floor.”

Videos posted to Twitter from people claiming to be witnesses showed people screaming and running for cover amid the sound of gunshots. The shooting continued intermittently for more than five minutes, according to the Associated Press.

“The gunfire never ended, it seemed like,” concert attendee Rachel Dekerf told CNN. “It just went on and on and on.”

Police converged on the area and blocked off roads. Some officers could be seen taking cover behind squad cars as other officers ran into the casino, the Associated Press reported.

Some of those with gunshot wounds were taken to University Medical Center, a spokeswoman told the Associated Press. Police urged everyone to avoid the south end of the Strip.

One of the victims was an officer with the Bakersfield Police Department in Southern California, according to a statement from the department.  Reports indicated that several of the department’s officers were off-duty and attending the concert when the gunfire erupted.