In the wake of an Illinois pediatrician’s suicide, investigators are looking into whether or not some of the vaccinations he gave his young patients were fraudulent, according to CBS Chicago.

Clues were found in a suicide note left by Dr. Van Koinis, which indicated there was a problem with the records he kept regarding the vaccinations.

“The note was very short,” said Cook County Sheriff Tom Dart. “It was a note where he expressed a lot regret and the note was solely driven at the fact that he did things he regretted as far as the vaccinations.”

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Dart added that Koinis expressed regret in doctoring the records.

“He was incredibly regretful for what he did and it was the only thing he mentioned in the suicide note. It was this and only this,” Dart said.

Koinis was reportedly a big believer in homeopathic medicine, and his suicide note mentions a span of about 10 years where he either doctored records or gave fake vaccinations.

Watch CBS Chicago’s report on the story below: