William Paul Thompson was born on May 2, 1938, in Wichita Falls, Texas. When he was very young, his family moved to New York. His father, William Webb Thompson, struggled with alcoholism. He often became violent when he drank, and this created a difficult home life for William. Because of his father's behavior, William began to feel resentment toward him. By the age of 12, he started drinking and stealing. As a result of these actions, he was sent to a reform school.

Throughout his life, Thompson found himself in trouble with the law many times. He was incarcerated in both state and federal prisons for various crimes, including burglary, forgery, safecracking, and counterfeiting. He claimed to have criminal records in several states, including New York, Florida, Texas, Pennsylvania, Georgia, and Kansas. When he was not in prison, Thompson traveled across the country and held several odd jobs. Some of these jobs included boxing and working for the Salvation Army.

In the 1970s, Thompson got married. However, his marriage did not last long, as his wife passed away from cancer in 1982. After her death, Thompson became more violent, and he later claimed that he committed his first murders shortly after. However, these claims have never been confirmed.

On March 25, 1984, William Paul Thompson was at a bar called the Murderer's Bar in California with his friend Robert Herman Boyle. They met two brothers, Robert and John Pariset, and all four men spent the evening drinking together. Thompson grew annoyed with the brothers because of their loud behavior. Later that night, while at their campsite, Thompson shot John Pariset in the head and searched through the brothers' belongings.

After this incident, Thompson and Boyle decided not to report each other to the police. They traveled to Winnemucca, Nevada, where they parted ways. During this time, the police issued an arrest warrant for both men because a witness had seen them at the campsite. Thompson continued on, committing several robberies.

On April 21, 1984, Thompson shot a transient named Randy Waldron in the head multiple times. Afterward, he attempted to rob two women but fled when they fought back. He was soon apprehended by the police, who recognized his tattoos.

At his trial, Thompson was found guilty of Waldron's murder, along with other charges. He was sentenced to death. Afterward, he was extradited to California for the murders of the Pariset brothers. During his trial, his friend Boyle testified against him, explaining that Thompson had killed the brothers to rob them. Thompson eventually entered a guilty plea for these murders.

In the following years, he decided to drop all his appeals and expressed a desire to die with dignity. Before his execution, Thompson made claims about committing additional murders in different states, although these claims were met with skepticism. On June 19, 1989, he was executed by lethal injection in Nevada. In his last moments, he thanked the prison staff for allowing him to die with dignity.