Ronald Alain Janssen was born on February 6, 1971, in Boorsem, Belgium. He was the third child in a family of four. His father worked as a miner, while his mother was a housekeeper. From a young age, Ronald faced challenges at school. He was teased by his classmates because he had a lisp.

At home, Ronald's father was strict and often depressed. The atmosphere at home was very tense, and Ronald lived in fear of his father's anger. This fear affected his sleep, leading him to struggle with insomnia, a problem he would have throughout his life. There was a serious incident in which Ronald allegedly tried to harm his father by injecting him with a liquid that was not insulin.

In contrast to his father, Ronald had a strong bond with his mother, Hilda. Their relationship grew closer during times when his father was abusive. When Hilda decided to divorce, all four children chose to stay with her.

Ronald worked hard in school. He studied in Hasselt and Leuven and graduated as an industrial engineer with high honors in 1993. That same year, he met Natalie, who would later become his wife.

In 1996, Ronald and Natalie moved to Genk, where Natalie found a job. Ronald worked as a technical and production manager in a company before deciding to become a teacher in 1998. He taught subjects like mechanics and computer science at a school in Maaseik until 2000.

In the middle of 2000, Ronald, Natalie, and their daughters moved to a place called Loksbergen. There, Ronald started teaching at Herk-De-Stad, focusing on computer science, economics, technology, and applied mechanics.

His life took a difficult turn in 2006 when Natalie left him. After the separation, Ronald lived alone in Loksbergen. Neighbors sometimes noticed him walking by himself at night while the rest of the community was asleep.

Ronald Alain Janssen committed several serious crimes from 2007 to 2010. His first known victim was Annick Van Uytsel. On the night of April 27 to 28, 2007, Annick was riding her bike home when Janssen threatened her with a knife. He kidnapped her and took her to his house. There, he killed her using a hammer, and then drowned her to ensure she was dead. After killing her, Janssen hid her body. A search was launched for Annick, involving 70 police officers, 200 volunteers, and a helicopter. She was missing for several days before her body was discovered on May 3, 2007, in the Albert Canal. It was found weighted down with stones.

Janssen's next attack occurred on January 2, 2010. He met his neighbor, Shana Appeltans, and her boyfriend, Kevin Paulus, as they returned from a coffee shop. He retrieved a weapon and a flammable product, then forced them into their car at gunpoint. While they were driving, he instructed Paulus to stop at a secluded area. There, Janssen shot both Shana and Kevin multiple times. After the murders, he burned his bloodstained clothes and disposed of the ashes. Two days later, he was arrested and confessed to the killings.

In addition to these murders, Janssen admitted to committing several rapes between 2001 and 2010. He confessed to five rapes but is suspected of up to 20. During the trial, prosecutors presented evidence that showed he used a knife to threaten many of his victims.

Ronald Janssen faced trial starting on September 20, 2011. He was found guilty of three murders, kidnapping, and other crimes. The jury delivered a sentence of life imprisonment on October 21, 2011. He faced another trial in 2012, where he was convicted of additional rapes and violent acts but received no extra prison time due to his previous life sentence.