Skip to main content

The most prolific Dutch serial killers

Back of a Dutch police officer in uniform
Image: Dutchmen Photography /

Crime is generally quite low in the lowlands of the Netherlands. Street crime isn’t much of a worry and anti-social behaviour rarely troubles anyone outside of the very poorest housing estates. It’s a pretty safe place to live.

Organised crime, however, flourishes. Partly due to its geographical location, Dutch criminals - and those of Dutch descent - form an interconnected network of arms dealers, drug and human traffickers, diamond fencers and fraudsters that is collectively known as the ‘penose’. These criminals are, of course, in it for the hundreds of millions of Euros that can be made in illegal trading.

When it comes to the ultimate examples of interpersonal violence, however, the Netherlands is far from prolific. It’s not a country known for its serial killers. That’s not to say that it hasn’t birthed any, though.

Maria Swanenburg – 23 victims

Maria Swanenburg poisoned and killed dozens and dozens of her neighbours. Her kill count is believed to be 23, making her the country's most prolific serial killer ever. She was also guilty of poisoning at least 65 people. Some believe that number to be very conservative, with a few Dutch crime buffs claiming that she may have murdered up to 90 people.

'Good Maria', as she was ironically nicknamed, was a callous and cold-blooded killer, but her story is as much about poverty and desperation as it is about murder. Swanenburg was soon identified as the reason behind so many people falling ill and dying of cholera-like symptoms when the police saw that the superficially community-minded woman was financially benefiting from many of the victims after their deaths.

Swanenburg, whose favourite weapon was arsenic, was arrested in 1883 after a three-year spell of poisonings. She was given life in jail and died in 1915.

Frans Hooijmaijers - 5 victims

Known as ‘Fat Frans’, this ‘angel of death’ serial killer and former nurse was found guilty of the murders of five patients at a Kerkrade Hospital between 1970 and 1975. However, it's believed that he may have killed as many as 259 of his ailing patients.

Hooijmaijers first confessed to being responsible for 15 killings and claimed to have done all in his power to relieve the victims of their suffering. However, he then withdrew this confession, claiming that he was merely guilty of giving non-lethal dosages without authorisation.

In an attempt to paint himself as the victim at his murder trial, he tried to justify his actions by saying that he had done it while the patient was either restless or in pain and that he did not know what to do because there were allegedly no doctors nearby.

He was found guilty of five murders and locked up, although he was freed in 1987 after serving 18 years for his proven killings, living as a free man until his passing in 2006.

Willem van Eijk – 5 victims

Willem van Eijk or 'The Beast from Harkstede' was twice convicted for a total of five murders. He preyed upon sex workers, strangling and raping them.

With each victim, van Eijk got bolder and mutilated them worse and worse. His vile actions were the product of brain damage and childhood trauma which led to decades of unfathomably violent fantasies about the evisceration of young women.

He was given life in prison and died an incarcerated man in June 2019.

Hans van Zon - 5 victims

Johannes Marinus 'Hans' van Zon was born in Utrecht during World War II. Elly Hager-Segov was the killer's first known victim; she was fatally stabbed in July 1964, after refusing his sexual advances. Soon after, van Zon killed his homosexual lover, the film director Claude Berkeley,

Next, he killed Coby Van der Voort, his mistress, in 1967. He later boasted about the murder to a man called Oude Nol, a conniving ex-convict. Using this knowledge, Nol blackmailed van Zon into carrying out a string of robberies and killings on his behalf.

Van Zon was given a life sentence after being found guilty of murder. Oude Nol was sentenced to seven years in jail.

Aalt Mondria - 4 victims

Violent, paranoid and a substance addict, the Balkbrug-born Aalt Mondria was an unpleasant and unstable man even before he killed people. When news broke of his first murders, he became something of a Dutch hate figure. He was condemned to life in jail for three murders in 1978 but served only 15 years.

He was released, only to kill again. He was later given an 18-year jail term in 1998, following the murder of his girlfriend's 10-year-old son.

The second time around, the Dutch courts sent him down for life. In 2011 he died in prison from untreated hepatitis C.