Although I have never been shot with a shotgun, I would assume it would be much more painful than how that guy reacted. If I were to guess they dropped out all of the shot and what you see is the wad. Maybe it was a salt gun or perhaps a less-lethal round? Either way I don't think that was a real shell.
Oh yeah, I agree, IDIOTS!
EDIT: Another thing to back up what I had said. Look at the shotgun recoil. Seems fishy to me.