The pilot reported that he planned a flight in a single-engine airplane. He conducted the pre-flight and then during the start sequence, the engine's starter would not engage. He turned off the switches, set the parking brake, and exited the cockpit. He rotated the engine by turning the propeller slowly by hand, so the starter would engage. The engine started unexpectedly, and the airplane moved forward.

The airplane collided with a hangar and an electrical transformer box, and a post-impact fire ensued. The airplane was consumed by the fire, which prevented any examination of the cockpit, brakes, or electrical system.

The accident is consistent with an inadvertent engine start when the pilot rotated the propeller.