As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF, EXPERIENCED APU FIRE WARNING. CREW ACTIVATED APU FIRE BOTTLE, FIRE WARNING LIGHT EXTINGUISHED. AIRCRAFT RETURNED TO LBB AND MADE AN UNEVENTFUL LANDING. INSPECTED AND FOUND NO EVIDENCE OF FIRE OR OVERHEAT CONDITION. REPLACED FIRE CONTROL PANEL AND FIRE DETECTION UNIT PER BOEING M/M.