http://en.wikipedia.org/wiki/Edmund_Kemper
One of the most chilling things about him:
Oh and another:
Most sickening of all:

One of the most chilling things about him:
On August 27, 1964, Kemper shot his grandmother while she sat at the kitchen table putting the finishing touches on her latest children's book. When his grandfather came home from grocery shopping, Kemper shot him as well. Then he called his mother, who urged him to call the police. When questioned, he said that he "just wanted to see what it felt like to kill Grandma and Grandpa." Kemper was just 15 at the time.
Oh and another:
on one occasion he buried the severed head of a 15-year-old girl in his mother's garden as a kind of sick joke, later remarking that his mother "always wanted people to look up to her." He killed six college girls in this way, and would often go hunting for victims after arguing with his mother.
Most sickening of all:
In April 1973, Kemper battered his mother to death with a pick hammer as she slept. He decapitated her, raped her headless body, and used her head as a dartboard after putting her vocal cords in the garbage disposal. His murderous urges not yet satiated, he then invited his mother's friend over and killed her too, strangling her.
