My long time school pal murdered his mother with an axe thru the head when he was 19. I had been out with him drinking the previous weekend and stayed at his house. After killing his mother he continued to smash her head with the axe until she had no head left. He then took her body into the garden, sat her in a deckchair and made her a cup of tea. When his father came home he saw his headless wife in the chair and my friend was laughing and saying "why doesn't she drink her tea" over and over.
30+ years later he still sits in a cell in Carstairs maximum security mental institution in Scotland laughing and asking if mother has drunk her tea yet. Some of the old team still visit him.
This guy was 100% normal for the first 14 years I knew him. God knows what happened to him.