I can tell you're a new animator based on your Newgrounds account, so I'll give you some advice. First of all, try using different backgrounds for every scene instead of having only one. It just seems rather lazy to have only one with the characters changing spots on it. Secondly, be sure to put in sound effects whenever it's needed, like shooting a gun for example. You can do that by converting a YouTube video with gun sound effects into an MP3, and using it in your animation. And lastly, the animation needs to be improved on. The best I can tell you is to keep on animating and keep practicing. Eventually you'll be more comfortable with your animation program, and you'll be popping out great animations in the future. Good luck!