A German mother shot the killer of her young daughter midway through a trial on March 6, 1981.

A year earlier, Marianne Bachmeier’s daughter Anna was abducted by Klaus Grabowski, a local butcher.

He sexually assaulted and then strangled the seven-year-old before dumping her body on the shore of a canal.

Marianne Bachmeier shot her daughter’s killer. (Getty)

His fiancee turned him in to the police.

Grabowski was a previously convicted sex offender who had agreed to a chemical castration several years earlier in exchange for leniency for a previous crime.

But with the court’s permission, he reversed the castration with hormone therapy.

On trial for Anna’s murder, Grabowski said he strangled her after the seven-year-old blackmailed him.

Bachmeier was incensed with the allegation.

Bachmeier smuggled a handgun into a courtroom in Lubeck on the third day of the trial.

Klaus Grabowski murdered a seven-year-old girl. (Supplied)

She shot Grabowski six times, killing him instantly.

“I did it for you, Anna,” she said as she lowered her gun and surrendered.

“I wanted to shoot him in the face. Unfortunately, I hit him in the back. I hope he’s dead.”

She was charged with murder, but prosecutors later changed the charge to manslaughter.

Initially, the people of Germany sided with Bachmeier after her act of vigilante justice.

But opinion turned against her when tabloids detailed instances of her being a neglectful mother.

In the trial, Bachmeier’s lawyers argued the killing was not premeditated.

She was sentenced to six years in prison and freed after three.

Marianne Bachmeier was jailed for manslaughter for killing her daughter’s killer. (Nine Archives)

After her conviction, she revealed on a television talk show that the killing was not done on the spur of the moment and she had planned it in advance.

A friend later revealed she had practised the killing in the basement of her home.

Bachmeier died of pancreatic cancer in 1996, aged 46.

She is buried next to her daughter.