On July 7, 2020, about 1344 mountain daylight time, a Mooney M20TN airplane, Canadian registration C-GTVS, was substantially damaged when it was involved in an accident at the Central Colorado Regional Airport, Buena Vista, Colorado. The pilot was seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot stated that he was on a cross-country flight from Canada to California and stopped in Buena Vista to refuel the airplane. During the takeoff, the pilot did not establish a positive rate of climb and looked down to adjust the engine mixture and put on his oxygen nose piece. He stated that during the takeoff sequence he was not paying attention to his airspeed and altitude. The pilot looked up and the right main landing gear hit the terrain very hard at an estimated speed of 150 to 160 knots. The pilot attempted to maintain control, and the airplane came to rest on the runway. A postimpact fire ensued, and the pilot sustained serious injuries as he exited the airplane.The airplane sustained substantial damage from the postimpact fire. The pilot reported there were no mechanical malfunctions or failures that would have precluded normal operations. A witness, who was located at the airport, reported that he observed the airplane takeoff from runway 15 with no problems noted. The airplane then suddenly impacted the runway surface, and a postimpact fire ensued. The witness responded to the accident location to assist the pilot. The pilot reported to the witness that he "went to get his oxygen nose piece and impacted runway."