He first worked in the office of the U.S. Attorney for the Northern District of California in San Francisco,[18] where he rose to be chief of the criminal division, and in 1982, he moved to Boston to work in the office of the U.S. Attorney's Office for the District of Massachusetts as Assistant United States Attorney,[6] where he investigated and prosecuted major financial fraud, terrorism and public corruption cases, as well as narcotics conspiracies and international money launderers.[28]