Timeline shows family court battle before Seattle-area double murder-suicide
Court docs shed light on legal drama surrounding Mercer Island murder-suicide investigation
Court documents now painting a clearer picture about the family legal battle that surrounded four people killed in two cities that were just miles apart. A mom and her son were found dead at a home on Mercer Island on Tuesday, according to Mercer Island Police. That same day, two others were also found dead at an Issaquah house.
KING COUNTY, Wash. - Newly obtained court documents show a complex series of protection orders, weapons surrender rulings and guardianship decisions unfolded in the months leading up to the murder-suicide investigation involving four family members found dead on Mercer Island and in Issaquah.
Police have said the case appears to involve a homicide followed by a suicide across two homes.
While investigators have not released a motive, court records detail a prolonged legal dispute over the care and guardianship of a vulnerable adult that continued until just weeks before the deaths. Keep reading for a timeline of events that led up to the four deaths.
Background: Family, caregiving, early legal foundations
Court filings show Dominick "Nick" Cuvillier, an adult with Angelman syndrome and significant developmental disabilities, lived with and was cared for by his mother, Danielle Cuvillier, for most of his life. A durable power of attorney executed in November 2018 named Danielle Cuvillier as Nick’s attorney-in-fact, with successor agents listed if she could not serve.
After the death of Nick’s father in 2018, caregiving responsibilities increasingly became a point of conflict between Cuvillier and her older son, Mackenzie "Mack" Williams, according to later court declarations.
2023–2024: Escalating family conflict
Court declarations and supporting letters describe a deterioration in the relationship between Cuvillier and Williams beginning in 2023, with disagreements over Nick’s care, medical treatment and future living arrangements.
Several character letters submitted to the court in January 2025 describe Cuvillier as Nick’s primary caregiver and advocate, while Williams’ court filings describe concerns about Nick’s safety and care. These accounts were disputed and had not been fully adjudicated at the time of the deaths.
Jan. 16, 2025: Domestic violence arrest, immediate rupture
Court records show police were called to Cuvillier’s Mercer Island home on Jan. 16, 2025, during a confrontation involving Williams, Cuvillier and Nick.
Cuvillier was arrested on suspicion of domestic violence and later released. Competing accounts of the incident appear in court filings, with each side alleging aggressive behavior by the other.
Following the incident, Nick left his mother’s home and stayed with Williams.
Details emerge in Mercer Island murder-suicide investigation
Four family members are dead in a homicide investigation spanning two cities in King County, with police believing the murder-suicide was carried out between two homes miles apart in Issaquah and Mercer Island.
Jan. 17–30, 2025: Power of attorney dispute, weapons surrender orders
On Jan. 17, 2025, a new general durable power of attorney was executed naming Williams as Nick’s agent, revoking prior powers of attorney, according to court filings. That document became a central point of dispute.
On Jan. 28, 2025, Cuvillier filed a petition for a vulnerable adult protection order against Williams, alleging abuse, neglect and personal exploitation. The petition sought immediate weapons surrender, citing Williams’ access to firearms.
That same day, the court issued:
- A temporary vulnerable adult protection order.
- An order to surrender and prohibit weapons, directing Williams to surrender firearms to law enforcement.
- Issaquah police later returned Nick to his mother’s home under court direction.
February – March 2025: Temporary orders reissued, compliance reviewed
Court records show the temporary protection order was reissued in February and March 2025, as the case continued, with the parties stipulating to extensions while awaiting further hearings.
A weapons surrender compliance review held in March found Williams not in full compliance, noting that while multiple firearms had been surrendered, at least one firearm purchase appeared unaccounted for. The court ordered no further hearings unless a full order was entered.
August – December 2025: Guardianship resolved, protection order terminated
In August 2025, the parties entered into a binding settlement agreement resolving the guardianship dispute.
On Nov. 10, 2025, King County Superior Court appointed Cuvillier as full guardian and conservator for Nick, granting her authority over his personal and financial affairs.
On Dec. 10, 2025, the court terminated the vulnerable adult protection order, citing the settlement agreement and dismissing the protection order case. Any related weapons surrender orders were also terminated at that time.
Police investigate Mercer Island murder-suicide, Issaquah double-murder
Two people have been found dead inside an Issaquah home, tied to a earlier murder-suicide on Mercer Island.
Dec. 30, 2025: Welfare check, Mercer Island deaths
At about 10:45 a.m. on Dec. 30, Mercer Island police responded to a welfare check at a home in the 8400 block of Southeast 46th Street after an attorney reported receiving a concerning email.
Officers found Cuvillier, 80, and her son Williams, 45, dead inside the home with gunshot wounds. Firearms were recovered at the scene.
Police said preliminary findings indicated a homicide followed by a suicide and stated there was no ongoing threat to the public.
Dec. 30, 2025: Issaquah welfare check
Later that day, Issaquah police conducted a welfare check at a related home and found two additional family members dead. Authorities reported no signs of forced entry.
Investigators said the deaths were connected to the Mercer Island case.
What investigators have not said
Authorities have not released:
- The exact sequence of events between the two homes.
- Which firearm or firearms were used.
- Whether the recently terminated court orders played a direct role in the deaths.
The King County Medical Examiner will determine the official causes of death in the coming days.
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The Source: Information in this story came from court documents filed in King County, the Mercer Island Police Department, the Issaquah Police Department and original FOX 13 Seattle reporting.