kinda fast for me to see what happened but it looked good. :D

Well, I can say that all of it is alright... BUT here's what you need to focus on in my opinion.

1. Gravity- The bullets for the shotgun should fall faster, ease in to give it a nice gravity effect with a motion tween.

2. Drawback- For both the victim and the killer move the bodies a bit. A Shotgun would force the shooter back a bit, and definitely so would the sniper... Keep in mind there are variables here such as floor stability, standing vs crouching vs laying down etc...
And as for the victim, the force of the bullet would force them back even more, and obviously they'll fall down at some point... Distance is a big one here, the closer the shot the bigger the explosion and the force.

3. Blood- Add some blood squirting outta the back of the head, I may not be right on, as I'm not a big madness/war animator, but a bit of extra blood never hurt anybody... wait

for your first animation that was pretty good.
let's see you add some length to your next flash.

it is a good start but likely to be blammed. you shouldn't submit experiments but wait to make a movie