What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) After starting the right engine the captain signalled the ground personnel to pull the chokes and disconnect the ground power unit (gpu) before he started the left engine. When the chokes were pulled the aircraft rolled forward stricking the gpu with the left propeller. The captain and first officer both stated that they were looking down to complete after start flows and checklists when they felt the aircraft roll. The parking brake was not set. Airman failed to use "before start" checklist. This checklist call for the parking brake to be set before an engine start.
As the FAA filed it
(-23) AFTER STARTING THE RIGHT ENGINE THE CAPTAIN SIGNALLED THE GROUND PERSONNEL TO PULL THE CHOKES AND DISCONNECT THE GROUND POWER UNIT (GPU) BEFORE HE STARTED THE LEFT ENGINE. WHEN THE CHOKES WERE PULLED THE AIRCRAFT ROLLED FORWARD STRICKING THE GPU WITH THE LEFT PROPELLER. THE CAPTAIN AND FIRST OFFICER BOTH STATED THAT THEY WERE LOOKING DOWN TO COMPLETE AFTER START FLOWS AND CHECKLISTS WHEN THEY FELT THE AIRCRAFT ROLL. THE PARKING BRAKE WAS NOT SET. AIRMAN FAILED TO USE "BEFORE START" CHECKLIST. THIS CHECKLIST CALL FOR THE PARKING BRAKE TO BE SET BEFORE AN ENGINE START.