Still a really strange way to try and fire a rifle. Not what one would instinctively do, given all the movies everyone must have seen showing people firing them in the more conventional manner.
Was going to let it pass, this being the picture thread and everything, but now you bring it up again, I did have the passing thought that maybe the shooter there was literally mentally disabled and someone put him up to it as a really mean 'prank', which would be a downright abusive thing to do. Hopefully they were just a common-or-garden dimwit, messing about.