https://www.cnn.com/2020/04/28/us/marty-smith-motocross-dead-trnd/index.html
RIP Marty.
A few other articles about his passing and his life. (There weren't many sources when I first posted because the news had just broken)
https://www.roadracingworld.com/news/ama-motorcycle-hall-of-famer-marty-smith-killed/
https://www.cycleworld.com/story/motorcycle-news/motocross-legend-marty-smith-killed-in-accident/