It was stupid to fire. He's not going to be able to hit the "fear for life" defense, and the castle doctrine is probably not going to apply.
The other factor is whether or not the shooter reported the other thefts to the cops prior.
But the fact that the kid was a Turk (not a German) and the excitement in Germany over all those gastarbeiters puts another kink in the mix. Why was this foreigner skulking around in a garage at Oh Dark anyway? Aren't exchange students supposed to be models of probity?
