As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED WHILE SITTING AT THE GATE WITH THE APU RUNNING NOTICED A HOT ELECTRICAL SMELL THEN SMOKE FILLED THE CABIN. A RAMP AGENT ALERTED THE CREW THAT THE APU WAS ON FIRE AND THROWING SPARKS. THE CREW UTILIZED THE EMERGENCY STOP AND FIRE TRUCKS WERE ROLLED. MX MEL'D THE APU PER EMB AMM AND THE APU WAS REMOVED AND REPLACED DURING NIGHTLY MX PER EMB AMM.