As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ALL ELECTRICAL POWER LOST WHILE AT GATE, FOLLOWED BY BURNING SMELL AND SMOKE IN COCKPIT. INSPECTED AC FOUND CB Q11 ON CPB1POPPED OPEN. INVESTIGATED AND FOUNDGCU#3 FOR APU IS BURNED ON THE INSIDE. GCU #3REQ REPLACEMENT. R&R #3 GCU IAW CRJ 900 AMM 24-22-03-000/400-801. OPS CHECK GOOD