On July 17, 1999, about 1400 mountain daylight time, an Anderson Rans S-12, N9230X, registered to and operated by the pilot as a 14 CFR Part 91 personal flight, collided with the terrain near Bowmont, Idaho. Visual meteorological conditions prevailed at the time and no flight plan was filed. The aircraft was destroyed by a post-crash fire. The private pilot and passenger were fatally injured. The flight originated from Nampa, Idaho, about 30 minutes prior to the accident. Several witnesses in the area observed the aircraft flying above the tree line, when the nose suddenly dropped and the airplane descended in a near-vertical attitude to the ground. One witness stated that he observed the airplane, approximately one minute before the collision, performing "S" turns along a road. The witnesses that heard the engine sound reported that the engine was "wound up;" "just a run-away motor, like airplane in a stall and full throttle," and "heard a different engine noise and then a thud." The Idaho State Police Officer who responded to the accident site documented the wreckage prior to rescue personnel's disturbance of the wreckage to remove the victims. The reporting officer stated that the nose of the airplane was pointing to the east. The fuselage remained upright. Fire damage was noted to the cockpit area and the leading edges of both wings. A groove located approximately one foot in front of the right wing was noted in the dirt. The leading edge of the left wing remained imbedded in the soil. The trailing edge of the left wing had folded forward. The mid-section of the fuselage was broken, or burnt away from the cockpit area. The tail section showed no visible damage. The horizontal stabilizer was in the "up" position. A Federal Aviation Administration Inspector from the Boise, Idaho, Flight Standards District Office, responded to the accident site and reported that the aircraft collided with the terrain in a nose down, left wing low attitude. Control continuity was established, and a trace amount of fuel was found in the fuel lines. The inspector reported that during a follow-up inspection of the wreckage, there were no mechanical irregularities noted. Vicki DeGeus, Coroner, Canyon County, reported that the pilot's cause of death was due to massive traumatic injuries. Toxicological samples were taken and sent to the Federal Aviation Administration Civil Aeromedical Institute, Oklahoma City, Oklahoma, for analysis. The results of the analysis identified Diphenhydramine in the pilot's blood and liver fluid.