Dith Pran... used to say: "I'm not a hero - I'm a messenger." ...[He was] a tenacious survivor of the 1975-79 Cambodian holocaust, when the communist Khmer Rouge slaughtered 1 million people- nearly a third of the nation's population- while the world looked on. He devoted the rest of his life to telling the story- best known through the 1984 film "The Killing Fields." Dith, a translator-photographer for Times correspondent Sydney Schanberg, remained behind after the fall of Phnom Penh to help report the Khmer Rouge takeover. But when Western journalists were forced to leave, Dith became a prisoner, spending...