What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
Aircraft was being returned to the pilot by mechanic after work was done by privacy data omitted at Boerne Stage.
Pilot started the engine at a higher than normal throttle setting and the aircraft started to move immediately after the engine started.
The pilot incorrectly handled the brakes for steering. The pilot steered a sharp turn to the right, then the pilot steered sharp left.
The leading edge of the aircraft's left wing then struck a pole and the momentum of the aircraft swung the craft around, causing the front of the aircraft to impact the west side of the FBO office building, which is also where the aircraft came to rest.
As the FAA filed it
AIRCRAFT WAS BEING RETURNED TO THE PILOT BY MECHANIC AFTER WORK WAS DONE BY ^PRIVACY DATA OMITTED^ AT BOERNE STAGE.
PILOT STARTED THE ENGINE AT A HIGHER THAN NORMAL THROTTLE SETTING AND THE AIRCRAFT STARTED TO MOVE IMMEDIATELY AFTER THE ENGINE STARTED.
THE PILOT INCORRECTLY HANDLED THE BRAKES FOR STEERING. THE PILOT STEERED A SHARP TURN TO THE RIGHT, THEN THE PILOT STEERED SHARP LEFT.
THE LEADING EDGE OF THE AIRCRAFT'S LEFT WING THEN STRUCK A POLE AND THE MOMENTUM OF THE AIRCRAFT SWUNG THE CRAFT AROUND, CAUSING THE FRONT OF THE AIRCRAFT TO IMPACT THE WEST SIDE OF THE FBO OFFICE BUILDING, WHICH IS ALSO WHERE THE AIRCRAFT CAME TO REST.