Mile Matić was born on 14 January 1956 in Derventa, in the Socialist Republic of Bosnia and Herzegovina, then part of Yugoslavia. His childhood was unstable and marked by family dysfunction. His father was an alcoholic, and his mother abandoned the family when Matić was three years old. He later settled in Doboj, where he spent most of his adult life.

Despite his troubled upbringing, Matić demonstrated high intellectual ability and intense focus. His intelligence quotient was reported to be exceptionally high, and acquaintances described him as persistent, disciplined, and goal‑oriented. He worked as a prison guard at the “Novi život” prison in Zenica, and also practiced karate, quickly achieving a black belt. For a period, he served as a karate coach before being dismissed after stealing money from membership fees.

Matić led a double life. Socially, he was described as calm, polite, and somewhat narcissistic. He was known to enjoy crime novels, luxury cars particularly Mercedes‑Benz and the attention of young women. Privately, he engaged in increasingly exploitative behavior. As an amateur photographer, he photographed young women nude, filmed explicit material featuring himself, and later blackmailed some of the women by threatening to publish the images in newspapers.

In March 1985, Matić began a relationship with Smiljana Vasiljević, then a third‑year high school student whose boyfriend was serving in the army. When she ended the relationship later that year, Matić became obsessive. He began stalking her, waiting near her school, and attempted to pressure her parents into arranging a marriage. When it became clear that the relationship would not resume, he escalated to open threats against Smiljana, her parents, and her boyfriend. He reportedly told her friends: “She will not live to see the eighth of March.”

During this period, Matić accumulated numerous complaints for threats and aggressive behavior, both privately and at work. These warnings were repeatedly dismissed or ignored.

Matić had been hospitalized at the Zenica Psychiatric Hospital, where he was diagnosed with paranoid schizophrenia. After approximately two months of treatment, he was released on 16 January 1985, officially declared “cured.” He was explicitly forbidden from possessing weapons and ordered to report monthly to a disability commission. A subsequent psychological evaluation by the Sarajevo Institute of Public Health reached similar conclusions. Matić later stole and concealed these medical records.

Despite the restrictions, he retained access to firearms through his employment. In the months leading up to the killings, he expressed thoughts about eliminating people he believed were persecuting or “haunting” him.

The killing spree began on the morning of 26 February 1986 in Doboj.

Matić met his sister’s husband in his parents’ apartment, in a room he habitually kept locked. An argument escalated into violence. Matić struck his brother‑in‑law in the head with an iron object, wrapped the body in a sheet and blanket, and shot him five times with a service pistol.

He then left the apartment and entered a taxi. Near the Vranduk tunnel, Matić murdered the taxi driver with four gunshots to the head and disposed of the body in the Bosna River. He removed the taxi signage from the vehicle and drove to Zenica, where he reported for duty at the prison.

At the prison cafeteria, Matić briefly socialized with a colleague he rarely interacted with. The two agreed to travel to a nearby village under the pretense of meeting girls. Near the village of Jeline, Matić shot the colleague in the head, left the body in the car, and returned to Zenica by hitchhiking.

That evening, at approximately 9:00 p.m., Matić changed clothes and stole an M62 submachine gun, a pistol, and approximately 300 rounds of ammunition from the prison. Disguising himself as a municipal official, he hired another taxi and requested to be driven urgently to Vinkovci.

While traveling near Žepče, the driver grew suspicious and attempted to alert police at a fuel station. Shortly afterward, two police officers stopped the taxi. When the trunk was opened, Matić opened fire with two pistols, killing one police officer, wounding the other officer, and injuring the taxi driver. He fled into Žepče, attempted to hide in a barn, and briefly confronted police again before escaping by disguising himself in a security guard’s coat.

By 10:00 p.m., Matić returned to Doboj, where he hired another taxi to Poljice, later redirecting to Koprivna Donja, claiming he was visiting a girlfriend. He was dropped off around 11:00 p.m. and walked to the hamlet of Velika Rijeka.

There, Matić broke into the home of Smiljana Vasiljević by entering through the roof. Moving room to room, he opened fire, killing Smiljana, her mother, grandmother, and grandfather. Her 19‑year‑old brother attempted to flee but was beaten, struck with a pistol, and shot in the head, surviving with severe injuries.

Matić waited in the house for Smiljana’s father until morning, but the man did not return. At approximately 5:00 a.m., Matić killed the family dog, then set fire to the house, barn, and garage.

After leaving Velika Rijeka, he traveled to Zarječe, where he asked locals for shelter while waiting for a bus. His hosts offered him food and a bed. As news of the massacre spread, they realized his possible identity and restrained him with a dog chain. When asked if he understood what he had done, Matić replied:
“I know. I intended to continue.”