As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: AFTER SWITCHING TO EXTERNAL POWER LEFT ENGINE WOULD NOT SHUTDOWN USING FUEL CONTROL SWITCH. AFTER 3 ATTEMPTS, USED FIRE CONTROL SWITCH TO SHUTDOWN ENGINE. MAINTENANCE ACCOMPLISHED FIM 73-21-20-810-831-R00 AND PERFORMED SATISFACTORY OPERATIONAL CHECK PER AMM 28-22-00-720-801.