You also obviously have never lived in Texas. Unless things have changed greatly since I left, just the fact that the kid was in his house, was unknown. and made a sudden movement is enough. Heck, the "castle doctrine" applies not only to protecting people, but property. If you catch someone breaking into you car, parked in the driveway, and he starts running away with your property, you could legally shoot him to stop him from getting away with your property. At least, that's the way it was just a few years ago.
So if you can shoot someone running away just to keep him from stealing your stuff, what makes you think you have to wait until someone who is in your house at 2 AM without your permission threatens to attack you before you can do so?
great point.
Actually, I have lived in Texas. And the Castle Docrine does not permit murder.