Boy Wonder (2010) on Netflix

The teenager Sean Donovan is a brilliant but shy student that lives with his father Terry Donovan in Brooklyn. Sean has a trauma since he has witnessed the murder of his mother in a carjack nine years ago. Sean frequently goes to the precinct to see criminal photos expecting to identify the killer of his mother and he is an amateurish boxer. During the night, Sean secretly is a vigilante, seeking out brutal criminals based on the police files to eliminate them. The efficient police lieutenant Teresa Ames has been just promoted after capturing the notorious gangster Larry Childs and transferred to work in the Homicide Department in the precinct where Sean uses to go. When Sean helps Teresa to change her flat tire, she befriends Sean and leans his traumatic story. But when she notes that Sean was searching in the computer of the police department the pimp that was murdered, she suspects that the troubled teenager might be the vigilante that is killing in New York City.