"El pobre hombre no supo qué pasó."
Translation:The poor man did not know what happened.
Both are ok, although they mean something slightly different. There are some adjectives in Spanish that change meaning depending on whether they come before or after the noun. "El pobre hombre" means "poor" as in "The unfortunate man", whereas "El hombre pobre" means "poor" as in "The man of lower financial status".