If I saw someone steeling anything I would try to get that person caught or take care of it myself. I F-N hate thiefs.
I actually saw a young guy steel some crap at a Walgreens. I chased him out to the parking lot. Unfortunately the Mngt said they couldn't do anything unless they caught him actually doing it. I said "why don't you just tell the police that you did catch him the act?".. I don't know what they ended up doing, but at least I felt good about what part I played.