(CNN) The 2,246 fetal remains found in the Illinois garage of Dr. Ulrich Klopfer this month are from abortions he performed between 2000 and 2002, when he operated clinics in Indiana, authorities said.

Klopfer died on September 3 and his family was going through his belongings at his home in Will County, about 45 miles from Chicago, when they found the medically preserved remains, authorities said.

They were inside small, sealed plastic bags that contained a chemical used to preserve biological material, Will County Sheriff Mike Kelley told reporters at a news conference Thursday. They were in boxes that were mixed in with other storage boxes

"I can tell you, the 31 years I've been doing this job, I have never seen anything like this, ever. It is a strange, one of those once-in-a-lifetime things," he said.

Klopfer operated three abortion clinics in South Bend, Indiana, before his license was suspended in 2015. County officials estimated how long the remains had been preserved but did not provide details on how they determined they were from nearly two decades ago.

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