John William Cooper was born on September 3, 1944, in Milford Haven, Pembrokeshire, Wales. He was raised in a working-class family, and his father worked in the local shipyard. Cooper had a brother and a sister and grew up in a typical neighborhood. From an early age, he showed signs of behavioral issues, and many described him as troubled.

In school, Cooper struggled academically and often got into trouble. He became known for his rebellious nature and was involved in petty crime as a teenager. By the time he reached his late teens, he had already been charged with various offenses, including theft and assault. His criminal behavior continued into adulthood, as he faced additional charges between the ages of 17 and 21.

In 1978, Cooper won a significant amount of money from a "Spot the Ball" competition. He won £90,000, which is worth much more today. This win changed his life, but it also led to problems. Cooper developed a drinking and gambling habit, leading to violence and fights. The money he had quickly disappeared, and he began a life of crime that included multiple burglaries.

By the time he reached his late 30s, Cooper was well-known in his community for his criminal activities. He began to target homes in his area and had a reputation for being violent when confronted. His early life was marked by instability and conflict, contributing to his later actions.

On December 22, 1985, John Cooper killed Richard and Helen Thomas at their home in Scoveston Park. After murdering the siblings, he set their house on fire. This marked the beginning of a series of violent crimes attributed to him.

In 1989, Peter and Gwenda Dixon went missing while on holiday in Pembrokeshire. They had set out for a walk but never returned. Their bodies were found later, and it was revealed that Cooper had tied them up, threatened them with a sawn-off shotgun, and forced them to share their bank card details. He robbed Peter of £300 and shot both victims at close range.

In 1996, Cooper encountered a group of five teenagers in a wooded area. He threatened them with a gun and sexually assaulted one girl, while he raped another girl from the group. By 1998, Cooper had committed around 30 burglaries and participated in an armed robbery, demonstrating a pattern of escalating violence.

In 2011, Cooper was convicted for the murders of the Thomas siblings and the Dixons, along with his other violent crimes. He received a life sentence without the possibility of parole. Following his conviction, police looked into other unsolved crimes that might be linked to him. This included the suspicious death of Flo Evans in 1989, the murders of Harry and Megan Tooze in 1993, and the deaths of Griff and Patti Thomas in 1976, which had previously been classified differently.

Despite the evidence against him, Cooper launched appeals against his convictions. His initial appeal was rejected in 2012, and he made another request for a review of his case in 2023. Cooper was diagnosed as a psychopath and is currently serving his life sentence in prison.