A champion road racer, he was an Indianapolis 500 rookie in 1964, driving a car specially designed by Mickey Thompson to carry an increased fuel reservoir. MacDonald had confided to friends that while he did not like how his car handled, he was able to achieve competitive speeds and did not want to give up his opportunity to run in the 500. Starting in the 17th position, he lost control in the fourth turn near the end of the second lap. He struck a wall on the inside of the turn. His car, loaded with 80 gallons of gasoline, erupted in a terrible explosion and created an on-track inferno and chain reaction accident that included the cars of Eddie Sachs, Johnny Rutherford, Bobby Unser, and Ronnie Duman. Sachs was killed instantly. MacDonald survived the immediate impact, but died shortly thereafter at the hospital of lung damage from inhaled flames. Unser and Rutherford suffered burns but survived and each eventually became a 3-time winner of the 500-mile classic. Duman also suffered severe burns and would race until 1968, a victim of head injuries suffered in a race at Milwaukee.