A 26-year-old German man died this week after being poisoned four years ago by his 57-year-old colleague Klaus O. Mercury had been put in between the sandwich of the twenties, causing him to fall into a coma and eventually collapsed.

Klaus O. mixed mercury and other toxic substances for years by eating and drinking from his colleagues. Two employees have already suffered severe kidney damage.

Another colleague, the 26-year-old man who died this week, suffered brain damage and ended up in a coma. The facts happened at a metalworking company in Schloss Holte-Stukenbrock in the state of North Rhine-Westphalia.

The truth came to light in May 2018 when one of the employees found a white substance between his lunch. The company’s security footage showed how O. had put toxic powder between one of the sandwiches.

The management called in the police, after which the man was arrested. Afterwards, many more toxic substances were found in his house. The poison had no taste so that O. could strike unnoticed for years.

The German was sentenced to life imprisonment last year. Why he poisoned his colleagues is still not entirely clear. During the trial, a psychologist said that O. may have considered his victims as test animals.

The police are still investigating 21 suspected deaths since 2000. An unusually high number of perpetrators’ colleagues have died of a heart attack since that time.