Posted Monday, May 17, 2009 --- 10:00 p.m.

A man's body is found on an island in the Mississippi River, south of Prairie du Chien. The coroner rules his death was due to drowning, but investigators have always believed there was more to it!

Now, 15 years later, they're more convinced than ever --- and they want your help.

"There are certain cases in every law enforcement officer's life that you think back on it, and you think, what can I do different?"

The death of Brian Dietrich is one of those cases.

"What has happened in 15-16 years that maybe we can go back and solve this case."

Lauren Knutson retired from the Crawford County Sheriff's Department three years ago. But he never truly left the work behind him.

"This was just too good a case to let go. There were just too many question marks... too many red flags."

Memorial Day weekend. 1994.

Then-Lt. Knutson was on call.

"I got called out to a death investigation."

A man's remains were found a mile south of Prairie du Chien at the shore of Indian Isle in the Mississippi River.

"Home to maybe 15-20 residences at the most... "

A seasonal cabin dweller made the discovery after going to investigate a suspicious odor. The clothing and a wallet found nearby indicated the remains were those of Brian Dietrich.

"Well, I referred to him as Rambo," Bonnie Dietrich says.

Dietrich lived across the state line in Clayton County Iowa. He was the son of the local sheriff. He was known for his biker lifestyle....

"lived off of the land... "

...and he was a new father to a baby girl.

"October 30th was a very frigid night... He was going to take his little girl out trick or treating," his mother says.

But back in October of 1993, Dietrich never returned home from a regular trip across the river to Prairie du Chien.

"He'd came to town to sell ginseng."

Special investigator Knutson says in the evening, Dietrich, his girlfriend and her brothers were hanging out at a downtown bar... at the time called, The Schooner Bar.

"At some point in time, there was a disagreement," Knutson says, "There was a scuffle ... Brian was struck once by one of the brothers."

This is where the mystery of what happened to Brian Dietrich begins - at this bridge leading out of Prairie du Chien. He was last seen walking toward it, headed home.

"What we know is what the people with him have told us that night."

But Knutson believes people know more.

"If you had to put it on a scale of zero to ten, it'd be a ten."

Investigators say Dietrich's girlfriend reported him missing several days later, insisting he was in the river.

"All indications are Brian didn't jump into the river voluntarily. There was just nothing that ever said he was suicidal."

It would take until May of the following year for Dietrich's body to turn up... entangled in the roots of Indian Isle.

"I just keep pursuing it... whenever something pops up..."

Dietrich's mother refuses to give up hope.

"I want to find out... I won't settle 'til it's done," she says, "I'm not gonna settle for someone getting away with it."

...for the sake of their granddaughter.

"His daughter looks like him very much, she says, "It's like having him there."

...for the sake of justice.

"Hopefully people just start coming forward."

In ten days, it will mark 15 years since Dietrich's body was found.

Now, Wisconsin's Department of Justice is taking a fresh look at this case. If you have any information, contact the Crawford County Sheriff's Office or crime stoppers.

Crawford Co. Sheriff's Office
608-326-0241
Crime Stoppers
Toll Free: 866-779-7297
Or, 608-326-8933