Crowbar's audience at Maryland Deathfest on Thursday heard Windstein slam the fan after he made his way through security barriers and staff as the band performed their track Planets Collide. He was grabbed and removed by bouncers - but the action involved Windstein, who hadn't seen what was going on, being pushed sideways.

Video shows the frontman, who's focused entirely on his performance, being taken by surprise as he's forced away from his mic. He takes a few moments to realize what's going on, then aims a kick at the fan, who's being restrained by a security man. The song continues as the young man is forced off stage, still trying to make contact with band members.

But Windstain takes off his guitar and follows, appearing to aim a punch or throw something in the direction of the departing fan. After assuring a stage hand he's okay, he returns to the mic and asks: "Does anyone else want their f***ing head kicked in?"

Then he waves at his bandmates and shouts angrily: "Stop this f***ing song." He throws his mic stand away and continues: "I'm so sick of this sh*t. You've got motherf***ers like Randy Blythe - nicest motherf***ing guy in the world. Some a**hole goes into his office, f***s his world up, and the guy almost goes to prison in a foreign f***ing country."