Craterfish

The movie takes place in a time where books are banished and those who want books have to scavenge for them (think Fahrenheit 451), the man in a suit and gas mask hunts and kills people with books, and the man in the hoody and gas mask supplies the books. Halfway through the movie, the Suit Man realizes that he and the other guy are the same person, which is hinted at occasionally. I see the ending as a way of the Suit Man "giving in" per se, once he realizes the hypocrisy of his ways, he offs himself. His killing of people with books being personal or as actual work is intentionally oblique.