It's a shame, but theft does happen. A few years ago we had a TSA agent arrested at PDX, she was brazen enough to steal from the carry on x-ray area while screening passengers.
An airline I worked for also had an employee steal a passenger's bag, the employee walked thru the metal detector, then the passenger set it off and was delayed. The employee took both his work bag, and the passenger bag. The good thing was that he didn't know that they have cameras at the checkpoint, they rewinded it and had video of him taking the stuff.
I believe when the police did an investigation, he had all kinds of baggage in his house as well.
Sad really, but it is what it is.