Marianne Bachmeier was born on June 3, 1950, in Sarstedt, a small town near Hildesheim in Lower Saxony, West Germany. Her parents had fled from East Prussia after World War II. Marianne grew up in a strict and conservative household. Her father was an authoritarian figure with a history as a member of the Waffen-SS. He was a heavy drinker, and this often made their home life difficult. She experienced a tense atmosphere with her father's aggressive behavior. When her parents divorced, her mother remarried, which created additional challenges in Marianne's life. She often felt troubled and described her stepfather as dictatorial. Eventually, Marianne's mother kicked her out of the house.

At the age of 16, Marianne became pregnant for the first time. She gave birth to a child, whom she placed for adoption. By 18, she was pregnant again, this time by her boyfriend. Shortly before the birth of her second child, she was raped. This child was also placed for adoption.

In 1972, Marianne began dating the manager of a pub where they both worked. At 22, she became pregnant for the third time. On November 14, 1972, she gave birth to her daughter, Anna. Marianne raised Anna on her own, and often brought her to the pub. Marianne had a lifestyle that involved working late hours and sometimes going out after work.

Documentaries about her life later showed that she often left Anna alone during the day while she was working or recovering from her night shifts. Marianne was aware of her challenges as a single mother and considered putting Anna up for adoption. Friends described her as someone who treated Anna like a little adult, expecting her to handle many responsibilities on her own. Anna spent time sleeping in the pub while Marianne socialized. According to a friend, Anna was a lively child who did not have a happy family life.

On March 6, 1981, during the trial of Klaus Grabowski for the murder of her daughter Anna, Marianne Bachmeier entered the Lübeck District Court. She had smuggled a Beretta 70 handgun into the courtroom. On the third day of the trial, at around 10 a.m., she stood up, aimed the gun at Grabowski's back, and fired seven shots. Six of the shots struck him, and he died almost instantly. After the shooting, Bachmeier lowered her weapon and was taken into custody without resistance.

The event quickly gained significant media attention. Many people across West Germany supported Bachmeier's actions, viewing her as a mother seeking justice for her daughter. She received numerous letters, gifts, and flowers expressing public empathy. However, others believed that her act of vigilante justice was not appropriate in a constitutional society. As media coverage continued, opinions about her began to shift, especially after details about her earlier life and choices regarding her children became known.

On November 2, 1982, Bachmeier was initially charged with murder. After negotiations, the prosecution dropped the charge, and on March 2, 1983, she was convicted of manslaughter and unlawful possession of a firearm. The court determined that her actions were not premeditated. She received a six-year prison sentence but was released after serving three years.

Following her release, Bachmeier moved abroad. She got married in 1985 and later moved to Nigeria, where her husband worked at a German school. They divorced in 1990, and she then lived in Sicily, working as a hospice aide. While in Sicily, she was diagnosed with pancreatic cancer and eventually returned to Germany.

In 1994, Bachmeier gave an interview and published her autobiography. She discussed the shooting and her motivations for it. She admitted that she had thought about the act before carrying it out to stop Grabowski from allegedly lying about her daughter. She expressed no remorse for her actions.

Marianne Bachmeier died on September 17, 1996, at the age of 46, from pancreatic cancer. She is buried next to her daughter, Anna, in Burgtor Cemetery, Lübeck.