More than 20 people are dead and more than 100 others injured after a shooting near the Las Vegas Mandalay Bay hotel, police said Monday during a press conference.

The main suspect started firing an automatic rifle from the 32nd floor of the Mandalay Bay hotel at 10:08 pm (0708 GMT) at a crowd of people watching an outdoor music festival during a performance by country singer Jason Aldean, Sherriff Joe Lombardo said.

The shots continued for more than a minute, with hundreds of people taking cover and trying to escape the scene.

The perpetrator, identified as a local resident, was shot and killed by police in the hotel room shortly afterwards, Lombardo added.

Though US authorities believe the perpetrator was a “sole actor,” Lombardo said that police were also searching for Mari Lou Danley, identified as an Asian woman who was with the suspect at the time of the attack.

A witness at the event told dpa she heard multiple gunshots before fleeing, and said she “crawled over dead people” as she tried to get away.

Lombardo said that several off-duty police officers had been attending the country music festival and that at least two had been killed in the incident.

He added that, despite the “confusion and hysteria” in the wake of the shooting, reports about multiple shootings cannot be confirmed.