Richard Schlesinger (48 Hours Correspondent)

I learned, never let anyone's emotions cloud your vision when you're investigating a crime.

until you've had plenty of time to think about it.

I had seen many crime scenes where there was a lot of blood and gruesome sights, but none that bad.

I was at the Springfield Police Department in the major case office, and I heard the radio call.

Dispatch advises that the second victim that was at the scene was actually believed to be the intruder and that the husband had shot the intruder.

And I was like, oh, my god.

Donna, oh, my god.

He's laying on the floor.

From every case, you learn something.

And this one taught me.

You never take anything at face value, nothing.

Mark Winger was calling from his own home after his wife Donna was attacked on a hot August afternoon in 1995.

Almost everyone who knew Mark and Donna Winger... They were terrific together.

She was crazy about him.

...thought they were perfect together.

They were both respected and successful members of their community.

Mark was a nuclear engineer for the state of Illinois.

Donna was an operating room technician.

And both sets of in-laws were delighted when the couple got married in 1989.

The Wingers were eager to start a family.