Did you know that in the USA I can shoot you if you come on to my property and do not leave when I ask as well?
Try to avoid ad hominem.
Other than that, if you do not cite credible sources for an incredible tale, expect only idiots to believe you.
I think you also have to prove that he was causing some sort of harm/discomfort to you, or you could probably be charged with murder. I don't think the court would like you to explain to them that you asked someone to leave your property and then you just shot them. It wouldn't go down too well, I think.
Then again, that's just my way of interpreting the law. The judge has the right to do that.