As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON APU START ATTEMPT AT THE GATE IN SNA. SMOKE WAS OBSERVED COMING FROM APU COMPARTMENT. MTC OPENED COMPT AND OBSERVED THE STARTER GLOWING RED. FIRE DEPT DISCHARGED HALON INTO COMPT. CTC MTC ADVISED THERE WERE FLAMES INITIALLY WHEN DOOR WAS OPENED. REPLACED APU.