Life of St. Augustine, by Possidius, c. 5th century. Possidius, a friend of Augustine for over forty years, wrote a biography of Augustine’s life. Possidius himself was, like Augustine, a bishop in the church, presiding over Calama in the Roman province of Numidia. Possidius composed his biography of Augustine some time before the capture of Carthage in 439.
The Tertullian Project. http://www.tertullian.org/. The text of Life of St. Augustine is public domain.