Oates began that career with the New York Police Department. He walked a beat in New York's 19th precinct, located on Manhattan's Upper East Side. He worked his way up the ladder, and later held the position of second of command of New York's Brooklyn South Patrol Borough. In this position, he was in charge of 3,000 police officers and 700 civilians. He also served as commanding officer of the legal bureau of the New York City Police Department Cadet Corps. By the end of his 21-year career, Oates had become head of intelligence for the department. There, he was part of the executive staff of Howard Safir, the New York City Police Commissioner. He also arranged security for the Millennium Summit and was also in charge of U.S. presidential security arrangements.