Edward Capehart O'Kelley (1858 - January 13, 1904) killed Robert Ford, the man who assassinated Jesse James. The shooting (on the 8th of June, 1892)took place in a tent saloon which Ford owned and operated in the silver mining town of Creede, Colorado.
In less than thirty days, O'Kelley was convicted of murder. He spent ten years in prison as punishment for his crime.
Image online, courtesy the U.S. National Archives.