I was working at a gas station. Aside from a few long term employees, the turnaround was fairly high. Mostly kids from the local school trying to earn some money during vacations. One time they hired this dude who was usually working construction but needed something during the winter. Super nice dude, always helpful and already had experience with cash registers. But given I've grown up around sociopaths, there was this tingle in the back of my head that there was something off about this guy.
During your shift you have to keep copies of all receipts and separate trucks from regular cars. At the end, you comb through them and make sure none of the truck receipts slipped into the regular pile, wrap a paper around them and put date and your signature on it.
One day a bit of work piled up and I was stuck with other duties before finishing my shift. As I was finally about to finish, I noticed my reciepts were gone. I asked them whether he placed them somewhere else. He said he already did my receipts for me (wasn't uncommon and like I said super nice guy).
I go to the breakroom and see the pile of receipts with paper wrapped around and my signature on them???
I ask him if he signed it with my signature. He casually responds with, "Yeah, I know how to do all the signatures from all the coworkers here.", and I think to myself "Yep, there it is". I coumbed through the receipts again, clocked out and went home. And coincidentally never worked a shift with the guy again. And a few weeks later he got fired. He got caught refunding customer money to his own bank account (he had experience with registers).