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(Michael Lloyd/The Oregonian)

A Portland man serving 10 years in prison for hiring a hit man to kill his estranged wife – only to learn she turned the tables and strangled her attacker – has died behind bars.

Michael Kuhnhausen Sr., 65, died Friday afternoon at the Snake River Correctional Institution infirmary, in Ontario, the Oregon Department of Corrections reported on Monday.

Michael Kuhnhausen Sr.

Prison officials said Kuhnhausen died of natural causes. His ex-wife told The Oregonian on Monday that he died of prostate cancer that apparently had metastasized to the bone.

Kunhausen's legal troubles began in September 2006, when his wife returned home from her job as an emergency room nurse and was attacked by an intruder.

Susan Kuhnhausen, who now goes by Susan Walters, was attacked with a claw hammer and suffered bite wounds. But she managed to choke her attacker to death.

Michael Kuhnhausen, who had worked as a janitor at Fantasy Adult Video, pleaded guilty to solicitation of aggravated murder for hiring Edward Dalton Haffey to kill his wife with a promise of $50,000 in pay.

With Kuhnhausen's release date coming this September, his ex took drastic measures to prevent him from coming to kill her – or hiring someone new to do the job.

She told The Oregonian in April that she had installed an alarm system, laid gravel outside the house to hear footsteps, and planned to put up surveillance cameras. Walters also devised what she called a "run plan," to go into hiding.

And, if things went poorly, she also wrote a will.

On Friday, Walters breathed easier -- but she also felt sad.

"I don't mourn his passing," she said. "Instead, I mourn the life he could have had, if only he could have have opened his heart for those of us who cared about him."

In 2008, Walters won a $1 million lawsuit judgment against her ex for emotional distress. She told The Oregonian in April that she wanted to make sure Kuhnhausen didn't have enough money to hire another hit man.

"I've spent the last eight years hoping and praying he doesn't have any hidden funds anywhere," she said at the time. "I'm hoping he hasn't found someone in prison who said, 'You just hired the wrong guy.' "

Walters no longer sounded worried on Monday. She sounded gracious.

"Being an imperfect woman, I married an imperfect man thinking that we could love, honor and negotiate and have a good life together," she said. "But he had issues around abandonment, anger and anxiety that he couldn't overcome."

Walters said she joined the Kuhnhausen family in hoping he finds the peace he didn't find in this world.

-- Bryan Denson