More than 20 people are dead and more than 100 people injured in an attack at a country music festival in Las Vegas, a city sheriff says.
The main suspect, identified as a local resident, was firing an automatic rifle from the 32nd floor of the Mandalay Bay Hotel and Casino and was killed by police, police spokesman Joe Lombardo added.
Though authorities believe the suspect was a "lone wolf", Lombardo said police are also searching for Mari Lou Danley, identified as an Asian woman who was with the suspect at the time of Sunday night's (Monday AEDT) attack.
A tweet from the Las Vegas Metropolitan Police Department says they don't believe there are additional shooters on the loose.
Several officers from the Bakersfield Police Department were attending the Route 91 Harvest Music Festival and one was shot and taken to the hospital with non-life threatening injuries.
Thousands fled as bursts of gunfire could be heard for more than five minutes, a witness said.
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.
Videos posted to Twitter show concertgoers sheltering in places as gunshots rang out throughout the area.
University Medical Centre spokeswoman Danita Cohen said 26 people were admitted to the hospital and 14 were in a critical condition. All had suffered gunshot wounds, she said.
Some officers took cover behind their vehicles while others carrying assault rifles ran into the hotel and casino.
McCarran International Airport officials say all flights in and out have been temporarily halted.