John Marquis, American Grand Prize 1914

The original source reports this is a photo of John Marquis in a Sunbeam in the 1914 American Grand Prize. The race was held in Santa Monica. Marquis' mechanic was Harry Hough. They placed ninth but crashed before the finish.
 
Marquis is an obscure historical figure in the context of auto racing lore. Artist Peter Helck's The Checkered Flag is a ready resource and offers some insight. Marquis was British and the only foreign entry in the contest. Although he was not seen as a favorite, he was leading the race when this incident occurred on lap 33. Another report indicates that Marquis was carrying the maximum fuel load in an attempt to run the event non-stop. How this might have contributed to the center of gravity on his machine at the time is speculation.
 
Note from Harold Osmer: Marquis had just received the signal that he had moved into the lead and obviously overcooked the next turn. This happened at the intersection of Ocean & Wilshire, dubbed "Dead Man's Curve" by the Los Angeles press of 1909 in an effort to gin up interest in the races. No racer ever died at Dead Man's Curve during the Santa Monica Road Races of 1909-1919. That fellow on the extreme left in the image is a photographer. He snapped a shot at this very same moment.