Previously on Unsolved.

Acker claimed three men picked up Joe at McDonald's, and when they did, John was in the back seat.

Then they drove to Whitnell Park where John tried to run away.

So then Joe caught John and the other men assaulted John and killed him.

So you think Joe did this?

No.

I think Joe was a helper.

And the reason he used mental patients is because you can't take him to court.

Acker would take his theory about Joe the patient to John's family,

including his older brother Mark, and to the police,

and ultimately to the media.

This was to have been the end of our series, the Xerofile.

However, a few weeks ago, a man approached the Ziris, claiming to have information from a source

who may have been in Whitnell Park when John Zira died.

For Schoonover and other detectives today, Acker remains this confusing piece of the puzzle.

We know now that crimes like this will be revisited by the perpetrator.

It's their way of reliving it and continuing to derive pleasure from it.

But what does Acker's strange behavior mean for cops like Schoon over decades later?

I still think he's an extremely viable suspect in this case.

And we're going to see where that goes.

From the Milwaukee Journal Sentinel,

this is Unsolved, a murdered teen, a 40-year mystery.

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