Legal Issues...
Perhaps Flying Lawyer will hazard an opinion, but it seems to me that you are pretty much obligated to do something at this point. If you are knowledgable of potential safety issues and fail to report it to the authorities, isn't is possible that after a crash a family member sue you for not taking appropriate action? Besides, scammers need to be caught and punished. If they are ligitimate, then Tallguy's points are well taken and no harm done.