A Smart Way to Steal.... or Not so Smart?

We had an unusual theft tonight at about 5 pm. A mother—about 50 years old, white, brown hair, somewhat heavy, teenage son about 13 or 14, short hair, came in and loaded up armfuls of DVDs (I’m not sure what else) and a) took them behind a stack end to sort through them, b) got into the bathroom before we could stop her and c) practically ran outside the library with a very large bag bulging with DVDs. I was waiting for her outside the bathroom, followed her to the circ desk talking to her and watching to see if she was going to check out, and then followed her to the car her daughter was driving. I began telling her that I needed to check the contents of her bag the moment she passed the circ desk and repeated it until her daughter peeled out of the parking lot. She insisted that I was insulting her, had no right, etc., etc..