Film The Boondock Saints (1999) - Two Irish brothers accidentally killed mafia thugs. They turned themselves in and were released as heroes. They then see it as a calling by God and started knocking off mafia gang members one by one. Willem Dafoe plays the detective trying to figure out the killings, but the closer he was to catching the Irish brothers, the more he thinks the brothers are doing the right thing.
The Boondock Saints
Director: Troy Duffy
Writer: Troy Duffy
Stars: Willem Dafoe, Sean Patrick Flanery, Norman Reedus