Léon: The Professional

Léon is an Italian hitman (or "cleaner", as he refers to himself) in New York City's Little Italy working for a mafioso named "Old Tony". One day, Léon meets Mathilda Lando, a lonely 12-year-old girl. Mathilda lives with her dysfunctional family in an apartment down the hall, and has stopped attending class at her school for troubled girls. Mathilda's abusive father attracts the ire of corrupt DEA agents, who have been paying him to stash cocaine in his apartment. After they discover he has been stealing the cocaine, DEA agents storm the building, led by sharply dressed drug addict Norman Stansfield. During the raid, Stansfield murders Mathilda's entire family while she is out shopping for groceries. When Mathilda returns, she realizes what has happened just in time to continue down the hall to Léon's apartment; he hesitantly gives her shelter.