Police are investigating reports of one or more active shooters in the area.
One Las Vegas hospital reported treating at least 20 victims with gunshot wounds.
The Route 91 country music festival was taking place at the Mandalay. Hundreds of people were seen fleeing the area. The shooting took place at the end of a performance by Jason Aldean.
Witnesses reported hearing possibly hundreds of shots fired in rapid succession. Multiple ambulances were flooding the area to help victims.
Witnesses said they saw at least one officer possibly injured in the incident.
A groundstop was initiated for Las Vegas' McCarran International Airport for departing and arriving flights.
There were reports of active shooters at other hotels on the Strip, but those were not confirmed by authorities and it was not immediately clear if the reports were a result of the mass chaos in the area.
DEVELOPING: We will provide updates as more details become available.
We're investigating reports of an active shooter near/around Mandalay Bay Casino. Asking everyone to please avoid the area. #LVMPDnews— LVMPD (@LVMPD) October 2, 2017
Shooting in Las Vegas. People fleeing (video from the Mandalay Bay hotel) pic.twitter.com/hs98J5uK6T— Eiki Hrafnsson (@EirikurH) October 2, 2017
Video courtesy of Drew Akioshi. He was attending the concert at mandalay bay when shooting started. pic.twitter.com/mbyh9Y387q— David Sakach (@davidsakach) October 2, 2017