The Nun-Mask Armored Car Heist The Town
The armored-car robbery in Boston's North End (beat 23) is the film's operational midpoint -- the job where the crew's margin of error vanishes and the violence escalates beyond Doug's ability to control it. The nun masks, the most iconic visual element of the film, were born from the intersection of costume design and criminal psychology. The sequence ends with a car chase through the narrowest streets in Boston and establishes that the crew's luck has run out.
The nun masks came from a conversation between a costume designer and an FBI agent
Costume designer Susan Matheson knew that many of Charlestown's bank robbers had attended Catholic schools as children and been taught by nuns. She suggested to an FBI agent consulting on the film that someone from Charlestown might rob a bank dressed as a nun. The agent's response -- that it was "not a bad idea at all" -- confirmed the detail's plausibility and gave the production its most memorable image. (imdb)
The masks are rubber latex with attached veils, creating an image that is simultaneously comic and disturbing -- the familiar habit of religious authority twisted into a tool of violence. The irony is layered: men raised Catholic, taught by nuns, wearing the faces of their teachers while committing armed robbery.
The slow-motion shot of Doug looking at a boy is the sequence's emotional center
Just after Doug and Jem put on their masks before the ambush, the camera overcranks as Doug looks out his window and locks eyes with a young boy on the sidewalk. The boy stares in horror at the man in the nun mask holding an assault rifle. The moment is a visual echo of beat 1's title card about crime as inheritance: Doug is showing the next generation what Charlestown produces, whether he intends to or not.
The job goes wrong because a guard fights back
The armored car arrives late. The crew moves on the truck. A guard resists -- the kid Doug warned Jem about in beat 20, the one who wears his vest on the outside and tucks his pants into combat boots. Jem pistol-whips him and the crew takes the money, but a call has gone out. The guard's resistance is the variable Doug could not plan around, and it triggers the cascade that leads to the police chase.
The sequence replaced the novel's movie-theater robbery
Chuck Hogan's novel features a movie-theater robbery in the corresponding structural position. The adaptation replaced it with the armored-car job, which served the film better for two reasons: it allowed for the car chase through the North End, and it escalated the crew's use of force more dramatically. The theater robbery's elimination was likely also a studio-level decision to avoid negative associations with real-world theater violence. (thefilmstage)
The nun masks inspired real copycat crimes
The image proved so culturally potent that it was replicated in actual robberies. Two robbers dressed in nun costumes held up a TCF bank in Palos Heights, Illinois, in a daytime heist that was immediately linked to the film. The incident illustrated a recurring phenomenon in heist-film history: the feedback loop between cinematic robbery and real criminal methodology. (findlaw)