As far as art and animation goes, this is really good. The art style is rigid and really fits the dark undertone that the film shoots for, but the movements could be a little more fluid. You've definitely got the body and build for the men down, but I would do some work on the female character. She held herself too similarly to the men, which doesn't bring that contrast that people look for. She was also a little bulky. With the art style that you're using, i would like to see her almost over-dramatized and extremely feminine. A murderess should represent the sexy and dark part of the female stereotype. That would definitely put the HOT in GUNSHOT for this murder esque movie.
The arms were also a little awkward. It looked like you didn't know what to do with them. Just remember, the arms don't always have to be doing something. Sometimes just leaving them at the sides is better than having them awkwardly bent all the time.
The music for this was AWESOME. I love the gritty undertone and bass to help set up the fact that this is supposed to be a darker film. Its hard to find the right audio sometime, and im glad that you managed with what you had.
On the subject of audio, I'm not sure if there was a reason for the lack of audio dialogue, and the awkward animation kept me from reading their body language at the time.
All in all, this is definitely something that I would come back and watch if it were made into a series or even a short film.