Chaos erupted at a Chicago restaurant and performance space over the weekend, when a fight broke out on stage, leading to a security guard being struck in the head with a chair.

The incident unfolded Saturday night at City Winery, a popular restaurant and music venue in the West Loop.

“I was recording just because it just seemed like ooh something spectacular is about to happen,” said attendee AiJai Mahoney. “Yeah something spectacular happened alright!”

Mahoney was at the winery to see artist Jon Pierce when she noticed an odd interaction between a security guard and one of the dancers. In the video she recorded, Pierce was heard saying something from the stage. Moments later, the security guard turned aggressive toward him.

“It just happened so quickly,” Mahoney said. “He was shoving people. I think he was shoving women on the stage. It was just a kerfuffle on the stage.”

Video showed an additional security guard trying to escort the other guard off the stage while Pierce screamed for help. The guard’s aggressive behavior continued, knocking over tables of food and drinks and shoving customers as he moved through the crowd. Eventually someone off camera threw a chair at the security guard, and the fighting escalated before he was escorted out.

Jon Pierce posted a statement on Facebook saying in part, “I hate that this happened to us all! It was an amazing night! I’m in the twilight zone but in spite of adversity love never fails.”

City Winery released the following statement to NBC Chicago:

“There was an incident at Saturday night’s concert involving an employee of a 3rd party security firm contracted by City Winery. This was an isolated incident and we have taken steps to ensure that this does not happen again. We apologize to our guests and to the artist for the disruption of the concert.”

As of late Monday, it remained unclear if anyone was injured in the incident or if criminal charges will be filed.

“It seemed like whatever beef he had was personal or internal,” Mahoney said. “This is your job there should be protocols that you follow for whatever situations are unfolding.”