MADISON, Wis. (CBS 58) — A UW-Madison researcher has been charged after prosecutors say he intentionally placed laboratory chemicals in a coworker's water bottle and shoes because he believed the coworker had been disrespectful and was not following lab rules.

According to a criminal complaint obtained by CBS 58, Makoto Kuroda is charged with second-degree recklessly endangering safety and tampering with household products. The charges carry a combined maximum penalty of 16 years in prison and $35,000 in fines.

The investigation began after UW-Madison police were contacted about a suspicious chemical odor coming from an employee's water bottle at the Influenza Research Institute on Science Drive.

The employee told investigators he opened the water bottle April 4, took a drink and immediately noticed a bad taste before spitting it out. Days later, he noticed a similar chemical odor coming from shoes he kept inside his office. No illnesses were initially reported.

The water bottle was collected and transported to the Wisconsin State Laboratory of Hygiene. According to the complaint, preliminary testing produced a presumptive positive result for chloroform at a concentration high enough that initial test strips could not provide an accurate measurement. Investigators were told the result was concerning because chloroform dissipates over time, meaning the original concentration may have been higher.

Investigators later learned Kuroda allegedly admitted to coworkers and supervisors that he had put a substance in the employee's water.

According to the complaint, Kuroda emailed a supervisor in Japanese and wrote, "I did it. I have also informed the person himself. I am very sorry."

Kuroda allegedly told investigators he had become increasingly upset with the coworker over several workplace issues, including his belief that the coworker was not wearing required laboratory protective equipment and had acted disrespectfully toward him.

According to the complaint, Kuroda said he saw a half-full water bottle on the coworker's desk, retrieved a mixture containing paraformaldehyde, or PFA, and Trizol from a laboratory refrigerator and placed some of the mixture in the bottle. He also allegedly put the chemicals inside both of the coworker's shoes.

Kuroda allegedly told investigators he knew exposure to PFA could cause irritation, vomiting, dizziness and other health problems. He also reportedly acknowledged he expected the coworker to become sick.

"My aim was just, he feel bad," Kuroda told investigators, according to the complaint.

The complaint also alleges Kuroda researched harmful amounts of PFA and Trizol using ChatGPT on his work laptop before the incident.

Investigators said Kuroda told them he searched multiple times for information about amounts that could be harmful to humans and animals. According to the complaint, ChatGPT displayed warning messages during those searches, but Kuroda said the warnings did not cause him to reconsider his actions.

Police said Kuroda had unrestricted access to the chemicals and had worked with PFA for years.

The criminal complaint states Kuroda told investigators he understood the chemical well enough to use an amount he believed would make someone sick without killing them.