(CBS) — He’s the most notorious killer in Chicago history.

And John Wayne Gacy was known to have worked inside and around a Norwood Park home where his mom once lived.

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CBS 2’s Mike Puccinelli has exclusive video from inside that building on Miami Avenue.

It’s never-before-seen Cook County Sheriff’s Department video of the basement of a home where Gacy’s mom once lived.

“Was he digging out here at times? Yes, he was. Did he pour concrete there at times? Yes he did,” Sheriff Tom Dart asks.

For years, many have speculated that the executed rapist and killer may have buried some of his more than 30 victims underneath ground, where he once walked and worked in the basement.

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So, Sheriff Dart brought in the FBI and internationally renowned experts to help his department find out if Gacy had created another cemetery inside or around the modest apartment building.

The team used infrared cameras to look for the telltale heat signature of decomposing human remains. No signature was found. Radar detected an abnormality under a parking lot behind the home. Cadaver dogs were brought in.

The search in March was comprehensive. But the announced results haven’t stopped the curious from stopping by to see what some call the Gacy house.

That’s one reason why Dart is speaking out.

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“If you’re going there to find something in regards to Gacy you’re wasting your time,” he says.