At 2345 eastern time, the passenger in a Cessna 172K deplaned and was killed by the rotating propeller. The pilot was not injured. The flight was preparing to depart from Richmond International Airport for Laurel, Del. The pilot had started the engine in preparation for the flight when he realized he had forgotten to remove the wheel chocks from the left main landing gear. With the engine still running, the pilot asked the passenger to exit the airplane, walk behind it and remove the chocks. The passenger agreed, exited the airplane on the right side, and shut the door. The next thing the pilot saw was the passengers arms up in the air. The pilot said the passenger may have tripped over the wing strut and fallen backwards into the moving propeller.