As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) ACFT WAS SHUTDOWN IAW CHECKLIST. ON RESTART, THE MASTER SWITCH WAS TURNED ON AND THE ACFT ENGINE STARTED TO TURN OVER WITHOUT TURNING THE THE IGNITION KEY TO START POSITION. MASTER WAS IMMEDIATELY TURNED OFF AND STARTER DISENGAGED. INTERNAL PARTS OF SWITCH SHORTED OUT AND CAUSED STARTER TO BE LIVE ONCE MASTER WAS TURNED ON - KEY WAS IN THE "OFF" POSITION. NO INJURIES RESULTED. NEW SWITCH INSTALLED AND ACFT RETURNED TO SERVICE.