Harry Brown (movie)

Harry Brown is a 2009 vigilante action-thriller movie. It was directed by Daniel Barber and starring Michael Caine, Emily Mortimer, Iain Glen, Jack O'Connell and Liam Cunningham. It premiered as a Special Presentation at the 2009 Toronto International Film Festival. 
Plot.
Described as a "modern urban western" the titular Harry Brown (Caine) is an elderly widower and ex-marine who has lived to see his neighbourhood overrun by violent gangs, drugs and crime. 
When his best friend Leonard (Bradley) is murdered and the gang leader responsible walks free, Harry finds himself snapping. Soon, his desire for revenge leads to the unlikely vigilante facing up to the young thugs with terrifying results.