On the other videos, you see a guy in white who is a row behind. He keeps flipping the bird and pushing punk then ducking behind someone else. He does this 2-3 times before Punk snaps. What a tool. I think it was several fans being dicks that caused the reaction.
I can't see any evidence that the fan did anything, especially due to his astonished reaction. Most fans who get hit are usually provoking the wrestler, and when the wrestler reacts; are always just as angry as the wrestler. I'd expect WWE have promptly contacted the fan and wouldn't be surprised if they've offered free tickets for a future show, or some merchandise. It makes it so much worse that he did this ON CAMERA.
I'm not condoning it, but no fan should be pushing any talents and i blame the security who should have instantly jumped in (or even been heavier in this instance).