Robert Leroy Parker (April 13, 1866 – November 7, 1908), better known as Butch Cassidy, was a notorious American train robber, bank robber, and leader of the Wild Bunch gang in the American Old West.After pursuing a career in crime for several years in the United States, the pressures of being pursued, notably by the Pinkerton detective agency, forced him to flee with an accomplice, Harry Alonzo Longabaugh, known as the Sundance Kid, and Longabaugh's girlfriend, Etta Place.