On June 15, 2001, at 2315 central daylight time, a passenger was seriously injured after walking into the propeller blade of a De Havilland, DHC-6 Twin Otter, N30EA,after the aircraft landed at the Skydive Chicago Airport, Ottawa, Illinois. Visual meteorological conditions prevailed at the time of the accident. The flight was operating under the provisions of 14 CFR Part 91 and was on a visual flight rules (VFR) flight plan. The pilot and the five other passengers were not injured. The flight departed the Hastings Airport, Hastings, Michigan, at 2200 and had arrived at its scheduled final destination. The pilot stated: "At 10:00 pm central time N30EA departed from Hastings Michigan (9D9) on a VFR direct flight to Ottawa IL. (8N2) after a pilot briefing to passengers remain in their seats until the ok is given to exit the aircraft. The main door was closed and checked prior to take off. Weather was clear and dry with the flight planned to 1 hr. and 10 min. The aircraft landed on runway 21 at Skydive Chicago (8N2) at approx. 11:10 pm during the back taxi I again reminded the passengers to stay seated with their seat belts on. The aircraft was taxied to the ramp in front of the main hanger per directions of the ground crew. The signal was given to stop and shut down, at which point the parking brakes were set. Some time during the shut down sequence 2 passengers did open the main rear left side exit door and exit the aircraft one passenger walked towards the left wing tip and the second (.......) ran straight towards the left propeller and was struck by the spinning propeller. The engines had just been shut down (fuel levers pulled) however still had high rpm. I heard a noise but saw nothing. As per the ground crew she just ran into the back side of the spinning prop and the ground crew could not stop her. It was stated by one of the other passengers that she really had to use the bathroom and just bolted when the aircraft stopped." The injured passenger stated on the National Transportation Safety Board Passenger Statement form Part A: "It was dark out. I released my seat belt and exited the plane to proceed to the hangar. There was no ground support crew, stairway or ladder to exit the plane. There was no lighting. The pilot gave no commands prior to passengers exiting" On Part D the passenger stated: "I have found out the pilot deviated from his normal procedure and parked the plane heading the opposite direction that he always parked in the past. As it turned out, once you exited the plane, the direction to the hangar put you in a path directly into the propeller. We were given no commands as how to exit or what direction to go once we did exit." The ground crew aircraft marshaller and two other passenger statements are attachments to the factual report.