The pilot had taken a newlywed couple up on a ceremonial 'mile high' local pleasure flight as a wedding gift. He reported that during a maneuver he felt a 'shudder', and elected to make a low pass over an airport taxiway, by some friends on the ground with a hand-held radio, for a 'landing gear check'. During the second pass the pilot asked the couple to 'look to the right where the moon shines over Barnwell.' The airplane collided with a spectator on the taxiway. A passenger stated that the pilot then 'freaked out' and was in no condition to fly the airplane. During a subsequent landing attempt, a passenger prevented a go-around by forcing the yoke forward and pushing on the brake pedals with his hands. The passenger stated the pilot 'wanted to keep flying and he was going nuts.' The pilot fled the scene after the accident but returned later. The pilot had arranged to have the people on the ground 'moon' the airplane during the low pass.