The helicopter was engaged in a partial power toe in landing to disembark two passengers. The passenger on the left side walked uphill, and was struck by the main rotor blades, sustaining serious injuries. The helicopter sustained minor damage to the rotor system, and the pilot relocated to a safe landing site. According to the other passenger and the pilot, the passengers had been briefed to not walk uphill when exiting the helicopter. The pilot stated that his attention was diverted between the passengers on each side of the helicopter, and maintaining the helicopter's position.