(CNN) -- Gunfire erupted early Monday at a club in Playa del Carmen, Mexico, leaving at least five people dead and a dozen others injured, according to government sources from the state of Quintana Roo.
The shooting broke out at an electronic music festival that had drawn visitors from around the world to the beach resort city.
Video of the aftermath posted on social media showed frantic club-goers rushing into the street as rescuers arrived at the scene.
Authorities in Quintana Roo say they're still trying to determine who was behind the shooting.
On a Facebook page for The BPM Festival, a 10-day electronic music event that was closing Monday, organizers said a lone shooter had opened fire in front of the Blue Parrot club. Three members of the event's security team were killed trying to protect patrons inside, the festival said.
The festival's statement said four people had been killed in the shooting. Officials could not be immediately reached to explain the discrepancy.
"We are overcome with grief over this senseless act of violence and we are cooperating fully with local law enforcement and government officials as they continue their investigation," the festival said.