Scream Bloody Murder (1973)
Matthew (Fred Holbert), a deranged young man, mangles his father with a tractor. During his fun, he loses his own hand. Afterward, he is placed in a hospital for the criminally insane. During his time there, he learns from a letter that his mother has found a new husband, which angers Matthew. He also gets his hand replaced with a hook, while in the hospital. Time passes, and he is eventually released. Unfortunately, he is far from being cured and goes on an unparalleled killing spree.