By Liz Collin

MINNEAPOLIS (WCCO) — It is the only unsolved homicide case in one southern Minnesota county, and a police chief is spending his retirement looking for new clues.

Someone murdered 21-year-old JoAnn Bontjes near Sherburn in 1975.

From old maps to yearbook pages, Don Mickelson has spent the last few years filling notebooks and folders with details about a young woman he never knew.

“She was a tough gal. She was a hard-nosed gal,” Mickelson said.

joann bontjes Retired Chief Continues Hunt For Young Salon Owner’s Killer

oAnn Bontjes (credit: CBS)

A popular hair stylist, Bontjes owned her own salon at 21. But after a night out at the Trimont Legion on October 1, 1975, she would never be back to run her business.

Bontjes’s car was spotted along Highway 4 south of Trimont. Nearly 40 hours would pass before a farmer would find her body a mile and a half away in a shallow ditch.

It is believed Bontjes was held captive before she was left alongside the road, badly bruised and shot in the head.

Mickelson spent 22 years as the police chief of nearby St. James. He never worked the case directly. But he has dedicated the last few years of his retirement looking for answers, hiring psychics, talking to people who have never been interviewed and posting his theories on Facebook.

don mickelson Retired Chief Continues Hunt For Young Salon Owner’s Killer

Don Mickelson (credit: CBS)

The case belongs to the Martin County Sheriff’s office. Investigators there told WCCO a sample pulled out of evidence within the last year from the Bontjes case has been sent to the Minnesota Bureau of Criminal Apprehension for testing.

Its team has conducted numerous interviews over the years as they continue to work the county’s only homicide case to remain unsolved — now for more than 42 years.

“I’ve got some people that are 90 years old or older who have been contacting me and said, ‘I’d like to see this solved before I die,’” Mickelson said.

Mickelson is offering a $3,000 reward in the case.

Anyone with any information about the death of JoAnn Bontjes is asked to call the Martin County Sheriff’s Department at 507-238-3166.