As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) WITH DOORS CLOSED ON STAND, ENGINES STILL SHUTDOWN, APU RUNNING WITH BLEED SELECTED. APU HAD BEEN RUNNING FOR APPROXIMATELY 5 MINUTES WITH THE BLEED ON FOR 2 MINUTES. SMALL AMOUNT OF SMOKE/HAZE NOTICED IN THE FLIGHT DECK, SHORTLY AFTERWARDS THE TOILET SMOKE ALARM SOUNDED. ALL PASSENGERS WERE DISEMBARKED. APU REPLACED.