`` Sin Nombre '' opens a window on Mexico 's Mara Salvatrucha gangs . Cary Fukunaga 's debut thriller set against backdrop of immigrant trafficking on trains . Fukunaga visited gang members in jail and rode an immigrant train for research . The film 's action includes a dramatic shootout scene featuring real gang members as extras alongside actors . The film is based on the book'El Narco:
`` Sin Nombre '' opens a window on Mexico 's Mara Salvatrucha gangs . Cary Fukunaga 's debut thriller set against backdrop of immigrant trafficking on trains . Fukunaga visited gang members in jail and rode an immigrant train for research . The film is based on the book'El Narco: