The Route 91 Harvest Country Music Festival in Las Vegas was marred by violence on Sunday when a gunman opened fire at the event.
Las Vegas Police have confirmed that they are investigating an active shooter situation at the Mandalay Bay Resort and Casino, next to where the outdoor festival was being held at the Luxor Hotel & Casino.
Several of the arists at the event took to Twitter to warn others about the shooting.
Jake Owen, who performed on Sunday evening at the three-day festival, took to Twitter later that night, writing, "Gun shots!!! Vegas. Pray to god. Love you guys. Love you Pearl."
According to eyewitness reports, at least one gunman opened fire on the attendees at the festival from the balcony of the Mandalay Bay using automatic weapons.
One festival goer posted a disturbing video of the incident, showing the concert in progress when what sounds like automatic gunfire disrupts the music.
Josh Abbot and Luke Combs were among other performers who also posted about the terrifying incident.
Abbot told fans that all members of the Josh Abbot Band were safe, and that they had been evacuated. He added, "My fiancée is still in the room. They won't let me in but she's safe."
ET will continue to update this story as it develops.