As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW INADVERTENTLY DEPLOYED THE PASSENGER OXYGEN MASKS DURING THE COCKPIT PREPARARION FLOW. ALL MASKS IN CABIN DEPLOYED, ALL PINS ARE STILL IN PLACE. CORRECTIVE ACTION: PERFORMED STOWAGE OF PASSENGER OXYGEN MASKS AS REQUIRED. REINSTALLED CARTRIDGES AND CLOSED DOORS. REF. EMB-545-MOD AMM 35-20-01.