Over the past few weeks, Machine Gun Kelly has fought UFC fighter Conor McGregor on a red carpet and struck a feud with heavy-metal icons Slipknot. And he must still be feeling feisty, considering that he threw a punch at a fan during the Louder Than Life Festival on September 26. MGK spent his headlining set getting booed and flipped off by festivalgoers in Louisville, Kentucky, a nonzero number of whom seemed to be Slipknot fans irked by his recent beef. And when Kelly went into the photo pit during a song, a few people appeared to jump the barrier and rush the rapper turned rocker, prompting him to deck one of them mid-song as security tried to hold them back. When he said, “Punch that motherfucker in the face,” he really meant it.