As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, SPARKS WERE NOTED EXITING TAIL PIPE, ACFT RETURNED TO AIRPORT AND LANDED WITHOUT INCIDENT, AFTER SHUTDOWN, ON PULLING ENGINE THROUGH FOR COOL DOWN THE ENGINE CAUGHT AND COULD NOT BE SPOOLED. UPON ENGINE TEARDOWN, THE COMPRESSOR DIFFUSER SEAL WAS FOUND TO HAVE MOVED ALLOWING CONTACT WITH IMPELLER. THE SEAL RETAINER WAS WORN AWAY UNTIL THE RETAINER RING RELEASED.