Mein served as the United States Ambassador to Guatemala during the Guatemalan Civil War. It was during his tenure that U.S.-backed state terrorism which started after the 1954 Guatemalan coup d'état greatly accelerated with forced disappearances and massacres. He was shot by rebels belonging to the Rebel Armed Forces (FAR) one block from the U.S. consulate on Avenida Reforma in Guatemala City on August 28, 1968. U.S. officials believed that FAR intended to kidnap him in order to negotiate an exchange, but instead they shot him when he attempted to escape. The rebels had killed two U.S. military aides prior to the assassination of Mein.
