EVERGREEN PARK, Ill. (CBS) — For nearly 30 years, a now-deceased suburban pediatrician told parents he was vaccinating their children.

Now, those families have new evidence that the shots were bogus. One mother told CBS 2’s Chris Tye on Tuesday she is angry, but not at the doctor.

“He was a little different,” one woman, Linda, said of Dr. Van Koinis. “He just didn’t think there was enough proof that the flu shots were worth it.”

But Linda liked Dr. Koinis. She said he was quirky and loving, and there were never any red flags that went up. Her son liked Dr. Koinis too.

“He had a cold all the time,” Linda said. “We were at the doctor’s quite a bit.”

So Linda took her son frequently to Dr. Koinis, and also frequently referred other families looking for a doctor.

But last August, police went looking for Dr. Koinis, who had gone missing. On Sept. 10 of last year, he was found dead of a gunshot wound in a Cook County Forest Preserve in Palos Township.

Like the branches of the forest preserve where Koinis’ body was found, red flags started to wave. Anger also started to flare, but not at the late doctor.

It is Cook County Sheriff’s investigators that Linda is angry at.

“You had five months to tell the parents,” she said. “What have you been doing for five months?”

She is angry at sheriff’s investigators for waiting five months, until Feb. 11, to share that Dr. Koinis left “a suicide note that raised questions about the record-keeping of vaccinations at his medical office” and evidence he “did not provide vaccinations to children at their parents’ request.”

Linda’s son received 20 vaccinations between October 2014 and January 2016 – for chickenpox, mumps, polio, and other standard preventable diseases. They were all administered by Dr. Koinis himself.

Last week, Linda tested her son to see if there is evidence in his system of those shots. He got 20 shots, and CBS 2’s Tye asked Linda how many of them were legitimate vaccinations.

“Well, none as of today,” she said. “None.”

Linda said she was always in the room when her son received the vaccinations. What does she think Dr. Koinis was injecting him with?

“Well, considering there was something that was a liquid – I mean, I’m not a doctor – I would say saline, maybe like, or placebos that are nothing,” she said.

Linda said she still feels bad for Dr. Koinis.

“I do,” she said. “I am not mad at him. I am not.”

But others who came to the now-locked-up office in Evergreen Park may be mad, or may be sick because of Dr. Koinis. There are drawers containing records of 28 years’ worth of patients who might rightly wonder what he injected them with.

“He was a great guy, but don’t love him more than you love your kids,” Linda said. “Get them tested.”

The Cook County Sheriff’s office told CBS 2 Tuesday night that they believed it would have been irresponsible to inform the public prematurely about the vaccination doubts without first conducting a thorough investigation.

Linda’s son is getting vaccinated for the first time this week. Some patients could be nearly 30 years old and not know they were never vaccinated.

If Koinis were alive, questions would swirl over insurance fraud, child endangerment, and medical malpractice. But Koinis is dead now and cannot be charged.

Yet, police said, for some reason they were not sharing Tuesday night, that their investigation remains open.