Police said Monday they believe the gunman who opened fire on concertgoers on the Las Vegas strip killed himself before officers broke into his hotel room.

"We believe the individual killed himself prior to our entry," Las Vegas Sheriff Joseph Lombardo told a news conference.

He said officers found "in excess of 10 rifles" upon entering the 32nd floor hotel room from which a gunman opened fire at concertgoers below, killing at least 50 and injuring hundreds