Danielle Cuvillier, Mackenzie P. Williams Suicide

Authorities in Washington are investigating what appears to be a complex murder‑suicide that claimed four lives across two affluent Seattle‑area communities. On Tuesday morning, Danielle Cuvillier, an 80‑year‑old artist, and her son Mackenzie P. Williams, 45, were found dead in a Mercer Island residence valued at $2 million. Later that day, police conducting a welfare check in Issaquah discovered two additional victims: Dominick Cuvillier, 34, and Williams’ wife, identified by neighbors and confirmed by family representatives.

Investigators are treating the Mercer Island incident as a homicide followed by suicide, though the identity of the shooter has not been publicly disclosed. The Issaquah deaths are being investigated as homicides, with both victims found shot and no evidence of forced entry. Police recovered multiple firearms: four inside the Mercer Island home and another in a vehicle at the scene.

Court records reveal that the tragedy followed more than a year of escalating family disputes centered on the care of Dominick, who had Angelman syndrome, a rare genetic disorder requiring lifelong support. After their father’s death in 2018, Williams coordinated caregiving arrangements with his mother, but later accused her of mistreating Dominick — allegations she denied. Legal tensions intensified in 2025 when Williams sought power of attorney over Dominick’s care, a move contested by Danielle, who claimed her younger son was being manipulated.

The conflict culminated in criminal charges, protection orders, and disputes over firearms ownership. Williams admitted to possessing 53 firearms, which he later surrendered under court order. Although a temporary caregiving agreement was reached in August 2025, granting Danielle guardianship while allowing Williams visitation, tensions remained unresolved. The investigation continues, with authorities piecing together how longstanding familial discord escalated into fatal violence.