As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE AT MSP UNDER EXTREME COLD CONDITIONS (MINUS 12 DEGREES FAHRENHEIT), RIGHT STARTER GENERATOR SHAFT SHEARED DURING START ATTEMPT. CAUSE FOR FAILING UNKNOWN. SUSPECTED COMBINATION OF TEMPS AND AGE OF SHAFT, THESE ARE NOT NORMALLY REPLACED AT OVERHAUL. INSTALLED OVERHAULED UNIT.