Halloween turned into a real-life horror movie in Madrid last night (Oct. 31), as three young women were tragically killed during a performance at Thriller Music Park by electronic musician Steve Aoki.

According to El Pais (via Spin), two of the victims were declared dead onsite, while the third died shortly after arriving at a local hospital. Two other concertgoers are in critical condition due to "trauma by crushing, possibly having suffered a fall and being trampled."

Details are still emerging, so there is always the possibility of inaccurate reporting, but what is known is that a stampede occurred at approximately 4AM. It's possible a flare set off in the crowd sparked a rush to the exits, where a massive bottleneck occurred due to only one of the exits being open.

"I was in the bottleneck that formed and it was inhuman," one attendee wrote on El Pais' Facebook page. "You couldn't move forward, because there were people lying on the ground, or backward, because people kept pushing. We were there for like half an hour, until it occurred to someone to open another door, and people began to exit that way."

The Madrid Arena was finally cleared out at 6:50AM, three hours after stampede began.