Toivo Harald Koljonen was born on 12 December 1910 in Lahti, Finland. Little is publicly recorded about his early childhood, family life, or education. He lived through a turbulent time in Finnish history, growing up in the aftermath of the country’s independence from Russia and the Finnish Civil War. His adult years were marked by growing tensions in Europe and the eventual eruption of the Second World War, which would set the legal backdrop for his eventual conviction.

Koljonen had a criminal past that eventually led to his incarceration. At the time of his most infamous crime, he was serving time at Riihimäki Prison. The reasons behind his initial imprisonment remain unclear in public records, but he was later transferred to the Huittinen auxiliary prison which is possibly as part of a broader wartime prison dispersal. Despite increased security concerns during the war, Koljonen managed to escape from the Huittinen facility in early 1943. While on the run, he attempted to avoid authorities by traveling through rural areas.

There is no available documentation suggesting he had any history of mental illness, political motives, or ideological beliefs that drove his crimes.

On 17 March 1943, after escaping from prison, Toivo Koljonen arrived at a remote farmhouse in Finland. The home was occupied by a family of five: a mother, two elderly grandparents, and two children. The father and the eldest son had both been conscripted into the army, leaving the rest of the family vulnerable and alone. Koljonen initially hid in the family's stable. It was there that he launched his first act of violence, using an axe to kill the daughter of the family.

After the initial killing, Koljonen entered the house and murdered the remaining four family members. His spree did not stop there — a visiting woman from the neighborhood, who happened to be present at the wrong time, became his sixth victim. All six individuals were killed using the axe, a weapon that would come to symbolize Koljonen’s crimes in the Finnish collective memory.

Following the massacre, Koljonen fled the scene but was soon located and arrested in Valkeakoski, not long after the murders. Given that Finland was under martial law during the wartime period, his crimes were treated with maximum severity. Koljonen was charged with six counts of murder and brought before a military tribunal or wartime court, where he was sentenced to death. His case stood out as particularly brutal even in a period marked by conflict and widespread violence.

On 21 October 1943, Koljonen was executed by firing squad at the Kärsämäki quarry in Maaria, near Turku. Notably, he was executed alongside convicted Soviet infiltrators.