A similar thing happened to my son however WAMU determined the 'fraud' was authorized (they believe he gave his PIN away -- which he didn't). So his claim for fraud has been denied ... what a mess.
The scam in his case is that bad checks were deposited at an ATM into his account (in the realm of $2000) then withdrawls (from $500 to $1500) were made at some Walmart stores. He was taken for over $8000.