Police are investigating and warning patients after a Chicago-area pediatrician's suicide note raised questions about vaccination records at his medical practice.

Cook County Sheriff’s police said they began investigating vaccination records from Dr. Van Koinis after he was found dead of a self-inflicted gunshot wound on Sept. 10 in a Cook County Forest Preserve in Palos Township. Police said a suicide note indicated potential issues with “the record keeping" at Koinis' practice.

“During the investigation into Koinis' death, including issues presented in the note, investigators found that discerning who received vaccinations and who did not was unclear due to record keeping issues,” the Cook County Sheriff’s office said in a statement.

They also discovered that, in some cases, Koinis did not provide vaccinations to children at a parent’s request.

“Out of an abundance of caution, Dr. Koinis’ former patients are encouraged to discuss this information with their current physicians and inquire about methods to test for prior vaccinations,” the sheriff’s office said.

Koinis’ practice was located at 3830 W. 95th St. in Evergreen Park, where he primarily served residents on Chicago’s Southwest Side and near southwest suburbs. State records show he had been licensed to practice in Illinois beginning in 1991.

An obituary for Koinis indicated he previously worked with Advocate Christ Hospital in Oak Lawn and Little Company of Mary hospital in Evergreen Park. OSF HealthCare said Koinis was "credentialed at more than one hospital."

"We were shocked and saddened to hear of Dr. Koinis’s death, and our thoughts and prayers go out to everyone impacted," OSF Healthcare said in a statement. "Dr. Koinis was an independent physician at a private practice. If contacted by law enforcement, we will cooperate fully. Any questions about the ongoing investigation should be directed to the Cook County Sheriff’s Office."

"The physician was in private practice and not in our pediatric medical group," Advocate Health said in a statement. "As pediatric health care providers, we do encourage parents impacted to contact their child’s pediatrician about vaccination concerns. If they need to find a pediatrician, parents can call 1-855-312-KIDS."

Police said an investigation remains ongoing and the Illinois Department of Public Health was notified.

Anyone with information about Koinis is encouraged to call the sheriff’s office at (708) 397-6366. Those looking for information about personal or family medical records can call a medical line at (630) 670-1673.