Sheriff's Office arrest Kent couple in connection with murder of woman found in burned car

Denise Kay Grigsby. - COURTESY PHOTO, King County Sheriff
Denise Kay Grigsby.
— image credit: COURTESY PHOTO, King County Sheriff's Office

King County Sheriff's Office detectives arrested a Kent couple Friday in connection with the murder of a 39-year-old Kent woman whose body was found in the trunk of a burned car May 6 near Black Diamond.

The Kent man reportedly had a dating relationship with both women and all three allegedly use methamphetamine, according to probable cause documents filed Saturday in King County Superior Court.

An argument among the three at the Kent couple's East Hill home in the 25000 block of 128th Place Southeast reportedly led to the killing of Denise Kay Grigsby.

Kennon Gregory Fastrup, 30, and Michelle Lee Backstrom, 34, each were arrested for investigation of first-degree murder and first-degree arson, according to probable cause papers.

The two are scheduled for a bond hearing Monday at the King County jail in Seattle. Both remain in custody at the county jail in Seattle.

Fastrup was in a dating relationship with Grigsby and also has an on and off dating relationship with Backstrom.

On the evening of May 4 to sometime on May 5, all three were at Backstrom's home when an argument broke out in the kitchen between Fastrup and Grigsby. Backstrom then entered the kitchen when the argument turned physical. The court documents did not indicate what the two were fighting about.

Backstrom told detectives that as she tried to break up the fight, Grigsby bit her thumb, which hurt and upset Backstrom. The fight between the two women continued in the garage where Backstrom punched Grigsby in the head and then grabbed a hard metal object and repeatedly struck Grigsby in the head.

Both Backstrom and Fastrup then used metal rope and a nylon key lanyard to strangle Grigsby, who died as a result of the injuries.

The couple then allegedly put Grigsby's body into the trunk of her own car and drove it to a remote driveway in the area of Southeast 328th Street and Southeast Auburn-Black Diamond Road.

Once at the site, the couple reportedly lit the car on fire with gasoline and fled.

Shortly after 4 a.m. May 6, Mountain View Fire and Rescue responded to a report of a car fire in the area of Southeast 328th Street and Southeast Auburn-Black Diamond Road.

When the fire department arrived the car was fully engulfed in flames. Fire investigators discovered the burned remains of Grigsby in the trunk of the car.

Deputies arrested the couple Friday in North Bend along Interstate 90 after a pursuit.

After her arrest, Backstrom confessed to the killing and arson and implicated Fastrup, according to probable cause documents. Fastrup told detectives he helped dispose of Grigsby's body via the arson but claimed Backstrom killed Grigsby at the house when he was gone.

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