Pettersson, three shots out of the lead to start the final round Sunday, drove just inside a hazard on the first hole. He made sure he could touch the grass with his club, as long as he didn't ground the club. He played out to the middle of the green, and PGA rules official Brad Gregory told him there might have been a violation.
After a lengthy video review, the PGA of America said a leaf moved as Pettersson took the club back. That's a violation of Rules 13-4c for moving a loose impediment in a hazard.
Pettersson was not notified until he left the fourth tee. He birdied his next two holes.