https://en.m.wikipedia.org/wiki/Mary_Bell
Read all about her through this wikipedia link. I first learned about this little devil on an episode of Deadly Women. Apparently when she was only 10 years old she murdered two little boys by strangling them to death and she would mutilate their genitals and carve her initials in their stomachs with an old pair of scissors. She of course had a horrific childhood being raised by a mother who was the town prostitute and she was subjected to abuse and neglect from her mother as well as child molestation from her mother's clients.
Real life can be so much more shocking and twisted than any scary movie or horror story.