What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) This incident occurred during a routine check hauling mission while at a level cruise of 40 miles east of Abilene, Texas, at an altitude of 4000 ft, on an IFR flight plan in VMC conditions. The upper half of the cabin door departed the aircraft. The rush of air removed the ATP rated pilot's headset from his head. The pilot was able to reestablish communications with center by plugging in a standard microphone and using the speaker. The pilot declared an emergency and landed in abi without incident. The missing cabin door has not been found to date. Post accident investigation failed to reveal any reason for the door to have departed the aircraft.
As the FAA filed it
(-23) THIS INCIDENT OCCURRED DURING A ROUTINE CHECK HAULING MISSION WHILE AT A LEVEL CRUISE OF 40 MILES EAST OF ABILENE, TEXAS, AT AN ALTITUDE OF 4000 FT, ON AN IFR FLIGHT PLAN IN VMC CONDITIONS. THE UPPER HALF OF THE CABIN DOOR DEPARTED THE AIRCRAFT. THE RUSH OF AIR REMOVED THE ATP RATED PILOT'S HEADSET FROM HIS HEAD. THE PILOT WAS ABLE TO REESTABLISH COMMUNICATIONS WITH CENTER BY PLUGGING IN A STANDARD MICROPHONE AND USING THE SPEAKER. THE PILOT DECLARED AN EMERGENCY AND LANDED IN ABI WITHOUT INCIDENT. THE MISSING CABIN DOOR HAS NOT BEEN FOUND TO DATE. POST ACCIDENT INVESTIGATION FAILED TO REVEAL ANY REASON FOR THE DOOR TO HAVE DEPARTED THE AIRCRAFT.