Badlands: a 1973 film based on a two month killing spree

This is a movie released in 1973 which is based on true events of the 1958 massacre in the South Dakota Badlands. It is an incredibly intriguing story about a man who, with his 14 year old female accomplice, goes on a two month killing spree. I discovered the movie after watching the original music video for the Bastille song, Flaws. This movie, if nothing else, proves that Martin Sheen is far more of a badass than his son ever will be.