As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RT ENGINE STARTER DRIVE GEAR SHAFT WAS DAMAGED TO THE EXTENT, THAT THE BENDIX COULD NOT RETRACT FROM THE ENGAGED POSITION. THUS CAUSING THE GEAR TO REMAIN ENGAGED AFTER START. THIS IN TURN BROKE THE DRIVE GEAR TEETH. THE BROKEN TOOTH THEN LOCKED UP THE RING GEAR CAUSING THE CRANKSHAFT TO STOP ROTATION. THIS CAUSED AN ENGINE FAILURE.