Henry John Burnett was born on January 5, 1942. Not much is known about his early childhood. However, he grew up in Aberdeen, Scotland. His life took a significant turn when he met Margaret May, a married woman with two children.

On February 2, 1957, Margaret married Thomas Guyan. They moved into a flat at 14 Jackson Terrace in Aberdeen, which belonged to Margaret's grandmother. Their first son was born in September 1958. A second child was born in February 1961, but the father of this child was not Thomas. This situation caused problems in the marriage.

By 1962, the marital issues between Thomas and Margaret intensified. Margaret sought legal advice about a divorce, but Thomas refused to agree. Later that year, Margaret began working at John R. Stephen Fish Curers. It was there that she met Henry Burnett. A romance developed between Margaret and Henry. By May 1963, she left her home with Thomas and moved in with Henry Burnett in Skene Terrace.

Henry John Burnett's story of murder began on May 31, 1963, in Aberdeen. On that day, Burnett locked his partner, Margaret Guyan, in their home. He believed she would leave him. When Margaret met her estranged husband coincidentally, she agreed to visit him. This upset Burnett when he learned of her plans.

Margaret went to her husband’s home to collect their son. A family friend named Georgina Cattanagh accompanied her. As soon as Margaret said she would return to her husband, Burnett became aggressive. He drew a knife and threatened Margaret. Cattanagh heard the commotion and banged on the door, demanding Margaret's release. After some time, Burnett fled the scene.

Burnett then went to his brother’s workplace. He told his brother about the incident, who advised him to go to the police. Instead, Burnett went to his brother's house. There, he broke into a cabinet and took a shotgun and cartridges. He boarded a bus back to where Margaret was staying.

Upon arriving, Burnett forced his way into the flat. Cattanagh shouted to stop him, but as Thomas Guyan came to see what was wrong, Burnett shot him in the face at close range. Thomas died immediately. Burnett then took Margaret at gunpoint. On their way out, he threatened a young boy they encountered.

Burnett forced Margaret to a nearby garage on Seaforth Road. There, he demanded a car from John Innes Irvine, who was filling his car with petrol. When Irvine tried to prevent him from stealing the car, Burnett threatened him with the shotgun. The police were alerted, and they began to track down Burnett.

Fifteen miles later, Burnett pulled over near Ellon. He offered no resistance when the police arrested him. His trial took place later that summer. Burnett pleaded insanity but was found guilty after a short deliberation by the jury.

Despite psychiatric expert testimonies about Burnett's mental health, he was sentenced to death for the murder of Thomas Guyan. On August 15, 1963, Burnett was executed by hanging. His execution drew a crowd of about 200 people outside the prison. After his death, Burnett was buried in an unmarked grave within the prison grounds, as was customary for executed prisoners. Years later, in 2014, his remains were exhumed and cremated.