You have the gun, and you have the dog. All you really need now is a reputation.
I totally agree with this.
The computer shop I work at has been grab-and-run shop lifted once. Just once. Between the fact that my boss chased the guy in his truck until the police managed to catch up and the fact that we go around wearing "fishing vests" all the time has kept things pretty smooth here even though we are not in the best neighborhood.
I think the poor running shop thief told his buddies.