This last week a few GI's from a local airbase decided it would be fun to drive around town and shoot at houses and cars with a 9mm, .357, and a 12ga.  This made me think, usually you are arming yourself for if someone came into your house.  In this case the person is on the outside shooting in.  Would I be in the right to return fire out of the house at the idiots?  After all, I would have bullets flying into the house how would I not think my life was in danger.

If you shot them coming AT your house, yes.
If you shot them going AWAY, no.
I think the law always frowns on shooting somebody in the back, no matter what the situation. You could've ran around the block though, and met them head-on!