I suppose this deserves a place in the Concept Art forum. Since it is simple, I guess it could be counted as practice. And that's what this forum area is about really.
You should've added on to the characters and made them more bulkier, more realistic, more detail, and should've extended the animation. Most animators make their animations as stick figures and then add on the detail after the animation is finished in stick-people-mode. I like how you made the lighting of the shot reflect off of the guys face. However I doubt an uzi would shoot a bullet that moves at such a slow speed. In fact, I honestly doubt a bullet moving that slowly would ever pierce some one's skin. Not only because it moves pretty slow for a fired bullet, but because of the bullet's shape. It's round like a ball!
~Craka_J