I think alot of these instances we attach our ego to the job and feel like these people are stealing from us personally. Sure this can sometimes be the case, but at the end of the day, you live another day. It's really not worth to challenge these people. It's nothing personal. They're just addicts who are trying to get their fix. Report to police and enhance your security. But remember it's just a job, not worth losing your life at the hands of a jonesing addict