My high school wood shop had large posters placed above most of the equipment that were just like that one. They reminded you of how dangerous the machenery could be if you didn't respect basic safety rules.
Who was the @$$ hole that didn't see that was about to happen?
The guy doing that demonstration just ain't the brightest either.... Look at where his hand is and the direction of the muzzle is when he cocks it :roll:
The bad thing is that injuries like that are seldom smart and happen very quickly. I actually didn't realize that the cylinder vented that much gas either, it stands to reason. Looks like it will leave a mark.