House of D (movie, 2004)

In the present, artist Tom Warshaw recalls his traumatic coming of age. As a 13-year-old growing up in New York City in 1973, Tom hangs out with Pappass, a mentally disabled man. With Tom's mother battling depression after the death of her husband, the young boy is left to his own devices. When Tom develops a crush on schoolmate Melissa, Pappass feels abandoned and begins behaving erratically.