As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS RECEIVED FOR IT'S SCHEDULED 100 HR INSPECTION, UPON COMPLETION OF THE PRELIMINARY INSPECTION THE FIN ATTACH BOLT AN4-6A THAT IS INSTALLED VERTICALLY THROUGH FITTING, PN: 0431009-3 WAS FOUND SHEARED. THE NUT AND SHANK OF THE BOLT WAS STILL PRESENT IN THE BOLT HOLE. IT IS UNKNOWN WHEN THE BOLT DECIDED TO FAIL. THE AN4-6A BOLT MOST LIKELY FAILED IN FLIGHT. OUR MAINTENANCE TEAM HAS INSPECTED THE SURROUNDING STRUCTURE AND RE-INSTALLED NEW HARDWARE. NO FURTHER DEFECTS NOTED.