John Cooper destroyed the lives of many people, including those of his own family. The twisted killer murdered siblings Richard and Helen Thomas in cold blood in 1985, then struck again four years later in a second sickening double killing of hikers Peter and Gwenda Dixon.
In both attacks, the evil killer tied up his victims then fired at them with a shotgun after trying to steal money from them.
It wasn't until decades later, when Cooper was behind bars for a string of violent burglaries, that the police came to a shocking realisation.
They were stunned to discover that darts fanatic Cooper had appeared on ITV gameshow Bullseye exactly a month before killing the Dixons and perfectly matched the artist's impression of the killer.
Read more on mirror.co.uk