The medical examiner says 56-year-old Duane E. Charley died of strangulation early Tuesday morning.
The Spokane County Sheriff's Office has arrested 30-year-old Amber I. Roberts in the attack. She is jailed for investigation of first-degree murder.
Details of the incident have not been released.
Charley was found dead on the floor in the hospital's forensics unit, where patients are evaluated after being committed by a judge during a criminal case.
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The union representing the direct-care workers at Eastern State Hospital in Medical Lake has issued the following statement about this morning's suspected murder of a patient:
"Eastern State Hospital workers, represented by Local 782 of the Washington Federation of State Employees/AFSCME, are deeply saddened by this morning's tragedy that took the life of a male patient. Losing a patient is like losing a member of our family.
"We are working with law enforcement through our agency on the crime scene investigation.
"We have been diligent in raising concerns about short-staffing on the wards at Eastern State Hospital. We have raised these issues with management for more than a year. It's not clear if this understaffing contributed to this morning's tragedy. Regardless, it doesn't bring back one of our family members, a patient in our care."
DSHS statement on death at Eastern State Hospital
Eastern State Hospital CEO Connie Wilmot confirmed that the Spokane County Sheriff's Department is investigating the death of a patient in the Forensic Unit at Eastern State Hospital.
The Spokane County Sheriff's Department is investigating in an effort to determine the facts surrounding the patient's death. Eastern State Hospital management and staff are cooperating fully as the Sheriff's Department conducts its investigation.
Administrative reviews of the death will be conducted once law enforcement has gathered the information they need to complete their investigation.
Patients have been moved off of the ward where the death took place and hospital management is providing needed support to patients and staff.