Boondock Saints

Two Boston Irish-Catholic brothers, Connor (Flanery) and Murphy (Reedus) McManus, turn into unlikely local heroes after the self-defense killings of some Russian mobsters who were threatening to close down their local pub. They turn vigilante, believing they're doing God's work to rid the world of evil, which leads to more slaughter. Investigating the crimes is gay FBI agent Paul Smecker (Dafoe), who is shown reconstructing the carnage in a series of flashbacks.