Man Arrested for Poisoning Co-Worker’s Drink After Losing Promotion

A shocking workplace revenge plot is making headlines after police say a Wisconsin man tried to poison his co-worker—then admitted to it.

Makoto Kuroda, 41, has been charged with recklessly endangering safety after investigators say he used lab chemicals to target a colleague at the University of Wisconsin-Madison’s Influenza Research Institute.

The case first came to light on April 7 when police were called to the lab over reports of a strange, chemical odor coming from an office. When authorities tested items inside, they found traces of hazardous substances.

Days later, police say Kuroda confessed.

According to court documents, he admitted to taking chemicals from the lab and placing them in his co-worker’s water bottle and even inside their shoes. Investigators say the substances involved included paraformaldehyde and Trizol—both potentially dangerous when mishandled.

It didn’t stop there.

Kuroda allegedly told police he knew how toxic the mixture could be, claiming that a larger dose could have been lethal.

In a message to another colleague after the incident, he reportedly wrote, “I did it. I have also informed the person himself.”

So why would someone go this far?

Authorities say Kuroda had ongoing frustrations with the co-worker, including minor workplace complaints. But the real motive, according to investigators, was much bigger—he was angry that the colleague had received a second promotion for a position he wanted.

Kuroda was arrested on April 10 and is being held on a $5,000 cash bond. He’s also been banned from the university campus and its laboratories as the case moves forward.

His next court appearance is scheduled for April 21.