This needs a lot of work.

First of all, remove all of the bullets and sound effects in the beginning. You let the song tell the story, not the effects. Secondly, your musical progression is horrible and slow. This sounds like a lame version of doom metal.

To improve, increase your tempo, and let the slow instrument (the guitar) symbolize power and dread. Let your drums symbolize weaponry. Also, get another guitar in there for rhythm.