If the dude was able to come up with a QR-code for an extortion letter, he/she is most likely IT literate
Umm - not so much. I used to know a guy who started a company creating QR codes for peoples' adverts, business cards, whatever. I think my shoes are more IT-literate.
Note - that does not make him a bad person. It just means he wouldn't know a MAC address from a serial number.