As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX - AFTER ENGINE SHUTDOWN AT GATE, AIRCRAFT BEGAN SHAKING, AND APU ENGINE PARAMETERS BEGAN CLIMBING. CABIN FILLED WITH SMOKE. SHUT DOWN APU MANUALLY. REMOVED AND REPLACED APU. COMPLIED WITH BLEED AIR DUCTING BLOW OUT. OPERATIONAL CHECKS GOOD. AIRCRAFT RETURNED TO SERVICE.