Sean Penn is an American actor, director, and political activist. He has starred in many films, including the 2008 biopic MILK, the 2001 drama I Am Sam, and the 2003 mystery-drama Mystic River. MILK tells the story of Harvey MILK, a gay rights activist who was assassinated in 1978. I Am Sam follows the story of a mentally challenged father trying to raise his daughter. Mystic River is a crime drama about three childhood friends whose lives are changed when one of them is murdered.