His point about leaving an area if it doesn't look right is explained in detail in a book titled The Gift of Fear, by Gavin de Becker, a security specialist who works mostly for governments and public figures, and is often called the nation's leading expert on the management and prediction of violence. The main point to the book is that if you get a bad feeling about a person or situation pay attention to that feeling and disengage from it. There's a lot of other good information in the book too. I would add that just because you carry a gun does not make it ok to ignore that feeling, because your gun is not a magic wand. I'd guess most of us here already know that, but there are others we might want to remind.
