On August 4, 1997, at 1120 Pacific daylight time, a Cessna 140, N2076N, being operated as a 14 CFR Part 91 personal flight, collided with a commercial building near the Evergreen Airport, Vancouver, Washington, shortly after takeoff. Visual meteorological conditions prevailed at the time and no flight plan was filed. The airplane was substantially damaged and the commercial pilot was fatally injured. The pilot rated passenger was seriously injured. Witnesses reported that the airplane had taken off to the west and attained an altitude of approximately 300-400 feet. The airplane then made a steep left turn. The witnesses reported that the wings leveled for an instant, then the nose dropped and the airplane descended in a near vertical attitude. The left wing of the airplane collided with the top of a commercial building and remained on the roof, as the rest of the airplane slid down the side of the building in a nose down attitude. The witnesses reported that the engine was running at the time of the accident, and that the engine sound did not change up to the time of the collision. Two mechanics at the airport reported that just prior to the accident, the pilot and passenger approached them and stated that during a flight in the pattern earlier in the day, the engine was "detonating" and experienced a "loss of power, then died." The mechanics reported that the pilot and passenger wanted to know what they thought might be the problem. The mechanics thought that maybe it could be a problem with the spark plugs, or maybe the magnetos. The mechanics stated that the pilot and passenger did not pursue the issue any further and began joking about getting insurance coverage. One mechanic did ask what fuel they were using and was told that it was a mixture of 100 and 80 octane. The pilot and passenger then stated that they were going to go and run the engine on the ground to see if the problem reoccurred. The mechanics did not have any further communication with the pilot and passenger and were not asked to look at the engine. A Federal Aviation Administration Inspector from the Portland, Oregon, Flight Standards District Office, inspected the engine and found that the number two cylinder exhaust valve appeared tight in the guide and the exhaust valve spring pocket contained excess carbon. The number three piston head showed signs of excess heat. There was no other evidence found to indicate a mechanical failure or malfunction. The Clark County Medical Examiner determined that the pilot's cause of death was due to blunt head trauma. Toxicological samples were sent to the Civil Aeromedical Institute, Oklahoma City, Oklahoma, for analysis. The results of the analysis were reported as negative.