Deranged is based on the infamous Wisconsin serial killer Ed Gein and was released in 1974. Roberts Blossom is Ezra Cobb who lives with his overbearing, ailing mother.
When she dies in front of him he is so grief stricken that after her burial he goes and digs up her corpse and brings it home (Ed Gein never dug up his mother though). He then starts robbing graves and murdering to have companions at his old farmhouse.