the 6 is for unoriginality
By style, your art is definitely worthy of good note, but this whole Gun-slinging killer thing is highly overdone, especially on newgrounds. If you really want to make this seem worthwhile, I can reccommend this:
1. give him some more compelling story... i.e. he's a hitman on a mission, or they killed his family, blah blah blah
or 2. Up the body count and make the killings grisly to the point of sadism. Newgrounds loves Sadism.