One Twitter user posted that the casino hotel was on lockdown, while another, citing police scanners, said two gunmen who had shot at a bodyguard and police were on the 32nd floor. Video clips posted online show what sounds like automatic weapons as panicked concertgoers are seen fleeing. Some dropped to the ground screaming.

(Disclaimer: this video below contains disturbing images and sounds)

Terrifying scene as concert goers attend to injured while gunman opens fire at Mandalay Bay resort in Las Vegas. pic.twitter.com/3bisNIjur2

- Josh Caplan (@joshdcaplan) October 2, 2017