On July 24, 2008, at 0915 central daylight time, an experimental Marshall James J, Cozy MK IV, N500K, single-engine airplane, was substantially damaged when it collided with the wall of a rock quarry southwest of Midlothian, Texas. The airline transport rated pilot, and sole occupant, was fatally injured. The airplane was registered to and operated by the pilot. No flight plan was filed for the local flight that had departed the Arlington Municipal Airport (GKY), Arlington, Texas, approximately 0700. Visual meteorological conditions prevailed for the personal flight conducted under 14 Code of Federal Regulations Part 91. According to an eyewitness located at the bottom of the 100 foot deep rock quarry, he could hear the engine of the airplane when it flew at high speed through the quarry at approximately 20 to 30 feet above the floor before it collided with the wall of the quarry and "exploded". A second witness reported that the airplane flew directly at his large bulldozer on the far side of the one mile wide quarry. The witness estimated the airplane was at 30 feet above the floor of the quarry when he waved at the airplane as it flew past him. The airplane was observed to bank to the right away from the bulldozer and then nose up to miss a large dirt pile. The airplane then collided with the quarry wall about 20 feet from the floor of the quarry. There was no post crash fire. The wreckage field began inside of the rock quarry about extended up the quarry wall and continued into an adjacent field. The quarry was approximately 100 feet deep with walls inclined about 23 degrees at the accident site. The debris field was approximately 100 yards wide by 350 yards long. Most of the airplane components were heavily damaged and were not identifiable. The landing gear was found in the retracted position. Due to the extent of destruction, control continuity could not be established. One of the propeller blades was separated from the hub, one blade fractured about 7 inches from the hub, and the third blade fractured 3 to 4 inches from the hub; signatures were consistent with engine power at the time of impact. The pilot applied for an experimental airworthiness certificate in July of 2004; at that time, a submitted weight and balance reported the acceptable weight and balance of the airplane 103.9 and 108.9 with an empty weight of 1,378 pounds and a CG of 117.87. A review of the airframe logbook revealed that the airframe was weighed on February 28, 2008 with a reported empty weight of 1,506 pounds and a CG of 83.7. The airplane was outfitted with a 220 horsepower Franklin 6A-350-C1R engine and Infinity retractable gear. An A&P mechanic reported observing an airplane which matched the description of the accident airplane overfly his home in Ovilla, Texas, approximately 9 miles northeast of the accident, about 0715. The airplane appeared to be flying at 2,000 feet above ground level in a straight and level attitude. Additionally, the A&P mechanic stated that the airplane's "engine sounded fine."