TMZ talked to Justin, who said he ran backstage between songs and hit the glass. He went back and finished his set, but after he returned to his dressing room he passed out for 15 seconds. That's bad, y'all. Doctors reportedly said he suffered a concussion but he'll be OK.
Weirdly enough, glass is a recurring foe in Justin's life. TMZ shared a video of Justin hitting his noggin on a revolving door. Glass is his Kryptonite!