Marianne Bachmeier was born on 3 June 1950 in Sarstedt, Lower Saxony, West Germany, to a family who had relocated from East Prussia after World War II. Her childhood was marked by instability and trauma. She was raised in a deeply conservative and religious household where her father, a former member of the Waffen-SS and a heavy drinker, often exhibited aggressive behavior. After her parents' divorce, her mother remarried, but the home life remained troubled under the authoritarian influence of her stepfather, whom Marianne described as dictatorial. Eventually, her mother forced her out of the house.

At 16, Bachmeier became pregnant with her first child, whom she gave up for adoption. At 18, she became pregnant again by her boyfriend, and this second child, too, was adopted. Her early adulthood was shaped by cycles of personal trauma, including sexual assault shortly before the birth of her second child.

In 1972, she began working at a bar called Tipasa and entered a relationship with the manager. At age 22, she gave birth to her third child, Anna, on 14 November 1972. Bachmeier raised Anna alone, often taking her daughter to the bar during her shifts and leaving her to sleep there late into the night. Friends later described the home life as troubled; Anna was treated more like an adult than a child, left unsupervised during the day while her mother slept after working nights. Bachmeier, aware of her difficulties as a mother, had reportedly considered putting Anna up for adoption at one point. Despite these challenges, Anna was remembered as a bright and lively child who longed for stability and affection.

On 5 May 1980, seven-year-old Anna Bachmeier had a fight with her mother and chose to skip school. That day, she was abducted by Klaus Grabowski, a 35-year-old convicted sex offender who lived nearby and whom Anna knew from previous visits to see his cats. Grabowski held her for several hours, sexually abused her, and ultimately strangled her with a pair of tights belonging to his fiancée. He then stuffed her body into a cardboard box and left it near a canal. It was Grabowski’s fiancée who later turned him in to the police.

Grabowski had a criminal record involving the sexual abuse of two girls. In 1976, he voluntarily underwent chemical castration, but later received hormone treatment to reverse the effects. At the time of Anna’s murder, he was on parole. Grabowski claimed Anna had threatened to tell her mother about the abuse and that he killed her out of fear of returning to prison.

The trial of Klaus Grabowski began in 1981 in the Lübeck District Court. On 6 March 1981, during the third day of proceedings, Marianne Bachmeier smuggled a small Beretta 70 pistol into the courthouse. At around 10:00 a.m., in courtroom 157, she pulled out the weapon and fired seven shots at Grabowski from behind. Six bullets hit him, killing him almost instantly. She lowered the gun and was taken into custody without resistance.

The act stunned the courtroom and immediately made headlines across West Germany and beyond. It became one of the most sensational cases of vigilante justice in the country's history. Public reaction was polarized — while many sympathized with Bachmeier as a grieving mother pushed to the edge, others viewed the act as a threat to the rule of law. Bachmeier sold her story to the magazine Stern for 100,000 Deutsche Marks, which she used to fund her legal defense.

Initially charged with murder, Bachmeier’s legal team successfully argued that the shooting was not premeditated. On 2 March 1983, after 28 days of trial, she was convicted of manslaughter and unlawful possession of a firearm. She received a six-year sentence but was released on parole after serving three.

Following her release, Bachmeier attempted to rebuild her life. She married a teacher in 1985 and moved with him to Lagos, Nigeria, where he worked at a German school. After their divorce in 1990, she relocated to Palermo, Sicily, where she worked in a hospice. Diagnosed with pancreatic cancer, she returned to Germany and lived out her final days in Lübeck.

Before her death, Bachmeier cooperated with journalist Lukas Maria Böhmer of Norddeutscher Rundfunk to document her final months. She also gave several interviews, including a 1995 appearance on the talk show Fliege, where she admitted that she had carefully considered the shooting and rehearsed it in advance. She never expressed remorse for killing Grabowski, whom she believed continued to lie about Anna even in death.

Marianne Bachmeier died on 17 September 1996, aged 46, in a Lübeck hospital. She is buried next to her daughter, Anna, in Burgtor Cemetery.