Thou needest to improve...
Okay, the idea seems solid, trick or treat children annoy the hell out of you and you get revenge. Im fine with that. But with a shotgun? Surely there would be a more inventive way of doing the dirty deed...like giving them a bomb shaped like a toffee apple, or give them some LSD that looks like candy or give them fruit...heh now thats evil.
Also, the graphics also need some improving as they aren't very good...I will presume that this is a first try, so for a first attempt not bad, but prehaps some characters would be good, or better still a plot...You remember those things?
Well, anyway, Thou must improve!!!