Auto speed king Mickey Thompson and his wife were shot to death this morning in the driveway of their exclusive hillside home in what authorities said was ``an assassination'' by two gunmen who fled on bicycles. Thompson, 59, and his wife, Trudy, were found dead at dawn by Los Angeles County Sheriff's deputies responding to reports of gunfire, said Deputy Doug Gatlin. ``It was a double homicide, an assassination,'' said Deputy Richard Dinsmoor. Neighbors said they heard 6 or 8 shots before the bodies were found about 6 a.m. on the driveway in front of the couple's Spanish-style home on Woodlyn Road in a high-security, gated community 20 miles northeast of downtown Los Angeles. They were shot to death, but the type of weapon wasn't disclosed, Dinsmoor said. The Thompsons were walking out to their van when they were ambushed. ``We don't know a motive,'' said Deputy Dan Cox. Doug Stokes, spokesman for Thompson Entertainment Group in Anaheim, said the Thompson's were apparently leaving the house for work when the shooting occurred. He said he didn't know of any threats against the Thompsons. Thompson became famous as the ``Speed King'' in the 1950s when he set the first of his nearly 500 auto speed and endurance records. In 1960 he became the first to travel over 400 mph on land when he drove a four-engine streamlined car to a speed of 406.6 mph at the Bonneville Salt Flats in Utah. He later turned to drag racing, Indianapolis car racing, won a national economy championship and was a top competitor in road racing and off-road championships in the United States and Mexico. He was a drag racing innovator, building and driving the sport's first ``slingshot'' dragster. He worked in the 1950s to take the sport off the streets onto sanctioned drag racing strips, and he was honored by the California Senate for his contributions to the youth of the state as well as the automotive industry. He was also well known as a promoter and his other sports activities included stunt flying and management of prizefighters. In pursuit of his land speed and Indy-car projects, Thompson often teamed with one of the auto industry's leading figures, Semon ``Bunkie'' Knudsen. Knudsen was a top executive with General Motors Corp. when he backed the Thompson effort to break 400 mph. Later, when Knudsen moved from GM to become president of Ford Motor Co., Thompson got company help with his own design of a Ford-powered dune buggy racer. As a racer, Thompson often failed to finish events because of mechanical breakdowns. He failed to finish in the first 27 powerboat races that he entered. He brought custom machines to Indianapolis racing in the early 1960s, but again the cars he designed were fast but not durable. Longtime friend Carroll Shelby described him as ``one of the greatest hot-rodders we've ever had'' and ``the dominant figure in off-road racing.'' ``He certainly had a colorful career,'' Shelby said. ``We're all going to miss him.'' When he was 12, Thompson ended his first race at Lakeland Park in nearby El Monte by crashing his four-cylinder Ford Model B hot rod against a wall during the first lap. He wasn't hurt because he was wearing a football helmet and was strapped inside with clothesline rope since he couldn't afford a real crash helmet or seat belts. Racing put him in the hospital 27 times, including a seven-month stay when he was paralyzed from the waist down after a boat racing accident. It was two years before he walked again. Thompson had a variety of other careers. He swept floors at the Los Angeles Times and later wrote sports articles there (``Just to see if I could.''), sold 10-cent hamburgers at a drive-in, produced and directed racing movies, owned 29 different businesses (``Every one of them has made money'') and was mayor of Rolling Hills. Danny Thompson, the couple's 37-year-old son who is also an off-road racer, wasn't immediately available for comment, said his publicist Carolyn Williams.