Until I read the later postings I thought it was that the old dude was getting robbed and shot his would-be robbers... maybe at a gas station or something. In that situation I was thinking that it was cool and stuff.
Only thing there would be the possibility of drugged up thieves killing otherwise-cooperative victims in gas stations, whatever b/c they assume that's the only way to get away with it...

Knowing more about it though, I wouldn't encourage that kind of thing. Even assuming the guys he killed were really bad people who are better off dead, it still leaves open too many possibilities for people getting hurt or killed who don't deserve it.