I thought the idea of space guns implied by that image was bad enough to claim the shark jumped. Using a regular old earth gun in space would be a bad enough idea on its own, and then you add in the rest of the nonsense.
A gun with a muzzle flare being fired in high atmosphere or beyond. WOO! That will certainly work and be a nice long scene!
Considering most gunpowder mixes have their own oxidizers, that would actually happen. But it's still stupid, because physics dictates that unless you lock yourself into the structure, firing a gun in space would almost instantly catapult you off said structure, or at the very least into another chunk of it, damaging you or your suit.
Guns developed for space would be more shotgun like, because the aim is merely to damage the suit, not the person inside it, because a damaged suit means death in space. That'd mean low-power high-spread ammunition that would not damage the delicate structures of space installations, but would be enough to punch a hole in a person's space suit or helmet. I suppose you could use the angle "this is the future" to call that the truth, and those guns in the video were all developed specifically for micro gravity use. It's still silly, though.
Accodring to Dr. L. Nelson of Bishop University c/o Slate.com.
In zero gravity, on the other hand, even the smallest recoil would send you backwards. In most cases this would be very manageable, however, bouncing you back at a speed of less than one meter per second, so you wouldn’t have to worry about seriously injuring yourself. Even if you fired a .44 Magnum, for example, and weighed only 100 pounds, the recoil velocity would be under 0.5 mph, which is still less than walking speed. If you wanted to really propel yourself using a gun, you’d want to use a really big one.
So they would push guys back ever-so slightly, but still enough to pull you out of cover. This COULD be compensated for by a jetpack and a smart program could be used to tell the suit to hold your position while you are firing if you are firing from cover, or you could latch a hip belt (or a leg) and translate the force to your cover (which might be enough in zero G to give it some rotation which would be interesting).
Anyway, I watched the video again and I only saw one astronaut firing and he was close enough to cover to be latched on to something.