Now that I've looked at it more closely, it is absolutely fake. Keep your eye on the guy with the earmuffs on. At the moment the blast occurs, his head and upper body turn a couple of degrees in a single frame. A less obvious giveaway is the lighting on the window toward the back of the room with the cannon in it. At the same moment that the observer's body shifts, the writing on that glass is suddenly lit from a different angle.
This is so fake, the way he flew back looks like it's straight from a movie. This would have probably broken the guys back or other bones if it was real.
