Police deputy James Barrigan was a police officer in the Boston Police Department and the best-friend of Colin Sullivan. He serves as the hidden tertiary antagonist of The Departed. He was one of two moles working for mobster Frank Costello. He killed Billy Costigan and officer Brown to stop Colin Sullivan, Costello's other mole, from being arrested. When Barrigan was not looking, Sullivan shot and killed him to cover his tracks.
- Both Barrigan and Sullivan are possibly a tribute to "Mafia Cops" Louis Eppolito and Stephen Caracappa, two Italian American NYPD officers who worked on behalf of the New York Mafia.