As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) HAZARDOUS EVENT DURING TRANSIT AT THE GATE, A FIRE WAS WITNESSED IN THE APU COMPARTMENT. THE FIRE BOTTLES WERE DISCHARGED BY THE CREW AND THE FIRE WAS EXTINGUISHED. THE ENGINE WILL BE REMOVED AND SENT TO REPAIR SHOP FOR INVESTIGATION.