SEATTLE, WASHINGTON – A devastating triple murder-suicide has claimed the lives of four family members across two upscale neighborhoods near Seattle, in what authorities describe as the culmination of a bitter legal dispute over guardianship. Police say the violence spanned two separate homes on Mercer Island and in Issaquah, with all signs pointing to a family conflict turned deadly.
At the center of the case is 80-year-old Danielle Cuvillier, a retired mother of two, who was found shot to death inside her Mercer Island residence alongside her 45-year-old son, Mackenzie Williams. Investigators believe Williams fatally shot his mother before taking his own life.
Two More Victims Found in Second Home
As investigators traced the family’s connections, they arrived at a second property in Issaquah later that morning. There, police discovered the bodies of Williams’ 34-year-old younger brother, Dominick Cuvillier—who had Angelman syndrome—and a woman believed to be Williams’ wife. Both had been shot. There were no signs of forced entry, and detectives suspect they were killed prior to the Mercer Island shooting.
Autopsies are underway to determine the precise timeline of the deaths. Five firearms were recovered across the two homes, including one found inside a car at the first scene.
A Family Divided by Guardianship Dispute
Court documents reveal that Danielle and Mackenzie had been involved in an escalating legal battle over who would assume guardianship of Dominick. In October 2023, a judge awarded full guardianship to Danielle, effectively ending Mackenzie and his wife’s control over Dominick’s care and removing them from the Mercer Island home.
Relatives close to the family told reporters the conflict had strained relationships for months. Investigators now believe that the loss of control and the ongoing dispute may have triggered the violent outburst.
Ongoing Investigation
While authorities have not publicly confirmed the order in which the killings occurred, they are working under the theory that Williams killed his wife and brother first at the Issaquah residence, then traveled to Mercer Island where he killed his mother and later died by suicide.
Police are continuing to interview witnesses, review forensic evidence, and piece together surveillance footage to determine a more accurate timeline. Official autopsy results are expected later this week.
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