Hoquiam detectives responded to the location and processed the scene with the assistance of patrol officers and the Grays Harbor Coroner’s Office. Investigators remained at the residence until approximately 0300 hours the next morning collecting evidence.
During the course of the investigation, multiple knives were recovered at the scene. However, only two appeared to have been used in the incident. All of the knives appeared to have originated from the kitchen where there was indication of a struggle.
There was no sign of forced entry and nothing appeared to be missing from the home.
Hoquiam officers had recently responded to the residence on October 30, 2012 regarding a disorderly conduct call over a family argument; there were no arrests made in the response. This incident was apparently related to an earlier reported incident to the Grays Harbor County Sheriff’s Office.
Earlier the same day, the sheriff’s office received a report that Mark Hinzman was accused of a sex offense which had allegedly occurred 12-15 years earlier in Central Park.
According to Chief Criminal Deputy Steve Shumate of the Grays Harbor County Sheriff’s Department, Mark Hinzman was being investigated and had been interviewed by detectives since the initial report on the 30th; the investigation was ongoing at the time of the homicide.
On November 14, 2012, the coroner’s office directed autopsies of both Mark and Mary Hinzman. The forensic pathologist concluded Mary Hinzman had suffered a defensive wound and several stab wounds which proved fatal; her manner of death was ruled to be a homicide
The pathologist determined Mark Hinzman died as a result of multiple self-inflicted stab wounds. His death was ruled as a suicide.
There was no note found at the scene. Both the sex offense investigation and the murder investigation were finalized by the death of Mark Hinzman.