As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE AT FL390, A MASTER CAUTION FLASHER AND "HYD O'TEMP B" AMBER CAS MESSAGE APPEARED, SHORTLY FOLLOWED BY A MASTER WARNING FLASHER AND "HYD O'TEMP B" RED CAS MESSAGE. AFTER ACCOMPLISHING EMERGENCY CHECKLISTS THE B HYDRAULIC SYSTEM WAS UNLOADED AND RENDERED UNUSABLE.