Since you said they were local, I wonder if this is what happened to you:
Credit card cloning, or "skimming" as it is sometimes called, is a technique whereby someone obtains your credit card details, copies them onto a bogus card and begins using the credit card. While credit card theft itself is not new, the manner in which the information is stolen is still not clear to many people.
A lot of time they put their "skimmer" on gas pumps.
https://www.google.com/search?q=cred...w=1260&bih=711