That's him on the left, Pancho on the right. He was a Federale from Sinaloa, an Indian fighter in Mexico's long war against the Yaqui, but in 1913 he hooked up with Francisco Villa and threw himself into the Revolution. He became one of Villa's most trusted lieutenants and, fairly quickly, a Major General at el Jefe's side.
Some highlights from the resumé of Rodolfo Fierro... On November 23, 1913, during the so-called Battle of Tierra Blanca, Fierro won the day by riding after a trainload of federal soldiers, climbing aboard, running across the roofs of the railroad cars, shooting dead the boilerman and the engineer, and bringing the locomotive to a screeching stop. Villa's forces then surrounded the train and killed over a thousand men; they also captured four locomotives, many horses and rifles, and 400,000 rounds of ammunition...
Then there was the time he got into a friendly argument with another Villista in Chihuahua... Fierro mentioned that when you shot a man, he invariably falls forward; his friend said, no, when you shoot a man, he falls over backward. They bet on it. Fierro drew his gun and shot a man walking toward them from across the street. The man fell forward and died face down in the dirt.
This photograph was taken shortly after they pulled the body out. (Chiefly to get the moneybelt full of gold coins, one assumes.) Handwriting on the back of the pic reads, "Rodolfo Fierro, number one killer and bodyguard of Pancho Villa."
And just so you know: He made it to the big screen. He was played by Charles Bronson in a 1968 movie called "Villa Rides." (Yul Brynner played Pancho.)