Quarter Horse jockey Sam Thompson died early Thursday of injuries suffered in a one-horse spill at Los Alamitos on Dec. 20, track officials said.\nThompson, 36, had been on life support at Los Alamitos Medical Center since the accident, but his condition deteriorated as the week progressed, the track said in a statement. His family chose to remove life support systems.\nThompson suffered upper-body injuries in the spill, which occurred after a 300-yard race for maidens. Thompson's mount, the first-time starter Harems Dynasty, broke down after the race and struck Thompson while he was on the ground.\nAt the time of his death, Thompson was surrounded by his girlfriend, Kristen Watanabe; his mother, Gloria Thompson; and trainer Donna McArthur, whose stable provided Sam Thompson with several of his significant wins.\nWatanabe said that Thompson was resuscitated twice after the accident.\n"His mother had an opportunity to come [from Maryland] to see him and so did his dad and brother," Watanabe said in a statement issued by the racetrack. "We were able to say goodbye to him in a proper fashion."\nA native of North Carolina, Thompson won more than 600 Quarter Horse races, including two runnings of the Los Alamitos Million Futurity - in 1997 with the champion This Snow Is Royal, and in 1999 with the champion Corona Kool. This year, Thompson was not among the leading riders at Los Alamitos after being sidelined earlier in the year with a broken foot. \nThompson won 55 stakes at Los Alamitos. In 2007, he won the Grade 1 Go Man Go Handicap aboard the champion FDD Dynasty. At Ruidoso Downs in New Mexico, he rode Big Time Hero to a victory in the 2006 Rainbow Futurity, the middle leg of that track's triple crown.\nThompson was active with the Jockeys' Guild at Los Alamitos and had a leadership role in the jocks' room.\n"He would always go to bat for a fellow rider," jockey Cody Jensen said in a statement. "He was never loud or boisterous, but when he had something to say, he held the respect of all the riders."