Sanna Sillanpää was born on 15 April 1968 in Finland. She completed advanced education, earning a Master’s degree in computer science, and worked professionally as an IT specialist — most notably for Fujitsu Finland Oy in Helsinki. By all outward appearances she was an educated, technically skilled professional.

Public reporting after the crime showed Sillanpää had an interest in popular culture (she was reported to enjoy The X‑Files) and — later in court proceedings — clinicians diagnosed her with schizophrenia. Prior to the incident there were no publicly documented, widely known violent offenses linked to her name. Her educational and employment background contrasted sharply with the brutality and surreal nature of the attack, which left investigators and the public searching for motive. In official psychiatric assessments conducted after the shooting, Sillanpää expressed delusional beliefs that were later described as involving vengeance for an FBI agent — a belief that formed part of the court’s psychiatric findings.

On 21 February 1999, Sanna Sillanpää rented a 9 mm Beretta 92FS semi‑automatic pistol at a shooting club on Albertinkatu in central Helsinki. While at the range she opened fire, killing three men and wounding a fourth so severely that he sustained lifelong injuries; a fifth man present escaped unharmed. One of those killed was the club’s 23‑year‑old supervisor. Witnesses later described the scene as sudden and methodical — Sillanpää firing multiple shots at people who were present for target practice.

As she left the shooting club, Sillanpää was reported to have said, “This is what they taught us at the FBI academy, isn't it?” That remark — bizarre and chilling in context — was later considered alongside psychiatric testimony. She then traveled by city bus across Helsinki to Helsinki‑Vantaa Airport, carrying the firearm and ammunition. At the airport she attempted to buy a ticket “to somewhere” and was intercepted while boarding an airplane bound for London about four hours after the shooting. Before boarding she discarded the pistol in a trash can in the terminal; it was recovered by a cleaner and matched to the weapon used at the range. When arrested she was cooperative but silent in court proceedings, speaking little or not at all.

Throughout the investigation and subsequent hearings, no clear external motive (such as a personal dispute with the victims) was established. Instead, repeated psychiatric examinations concluded that Sillanpää suffered from schizophrenia and harbored a specific delusion: she believed herself to be the widow of an FBI agent whose death she needed to avenge. This fixed false belief, and other psychotic symptoms, became central to the legal determinations that followed.

At trial the prosecutor initially sought criminal punishment on the basis of manslaughter (arguing partial insanity was not sufficient to avoid criminal responsibility), citing Sillanpää’s premeditation — for example, her attempt to flee the country and conceal the weapon. However, on 11 October 1999 the district court ruled Sillanpää legally insane, and that she could not be held criminally responsible under Finnish law. The Helsinki Court of Appeal upheld that decision on 11 October 2000. Rather than a prison term, the courts ordered forensic psychiatric care, and Sillanpää was committed to Niuvanniemi Hospital in Kuopio for treatment and security detention.

The shooting prompted immediate regulatory responses in Finland. The Ministry of the Interior reviewed and tightened security and admission rules for commercial shooting ranges, and first‑time participation procedures were made stricter to reduce the risk that unfit or unstable individuals could access firearms in a recreational setting.