As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON DESCENT, THE AUXILIARY POWER UNIT FIRE BOTTLE DISCHARGED WARNING LIGHT ILLUMINATED. *S/D* VISUAL INSPECTION NOTED THE AUXILIARY POWER UNIT FIRE BOTTLE PRESSURE WAS AT APPROXIMATELY 250 PSI, THE THRESHOLD FOR LOW PRESSURE INDICATION. REPLACED THE FIRE BOTTLE, AND RETURNED THE AIRCRAFT TO SERVICE.