As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IN-FLIGHT, PILOT HEARD A LOUD POP. LANDED AT THE NEAREST PLATFORM AND AFTER SHUT DOWN, FOUND FORWARD FLEXURE ON INPUT DRIVESHAFT HAD FAILED. ONE OF THE FORWARD FLEXURES FAILED AT THE BOLT HOLE AND A PORTION OF THE FLEXURE WENT THROUGH THE TRANSMISSION DECK/CABIN ROOF. (X)