As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED CABIN ALT WARNING HORN AT 10,000 CABIN ALTITUDE IN CLIMBOUT AND BOTH ENGINE BLEED SWITCH WERE IN OFF POSITION. O2 MASKS WERE DEPLOYED. EMERGENCY DECLARED FLIGHT RETURNED DFW LANDED WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. AIRCRAFT IS CURRENTLY UNDER MAINTENANCE.