On December 30, 2025, 34-year-old Dominick "Nick" Cuvillier Williams was found dead from gunshot wounds in a home in Issaquah, Washington. His death was part of a tragic series of events that spanned two cities and claimed the lives of three other family members in a murder-suicide. Dominick, who had a rare genetic disorder called Angelman syndrome and was mostly non-verbal, was a beloved figure in his Mercer Island community.
The investigation into the deaths began on the morning of
December 30th when police were called to perform a welfare check at the Mercer Island home of Dominick's mother, 80-year-old Danielle Cuvillier. The request for the welfare check came after her older son, 45-year-old Mackenzie “Mack” Williams, sent a concerning email to friends about his gun collection, hinting that they might encounter something traumatic at his house. At the Mercer Island residence, officers discovered the bodies of Danielle Cuvillier and Mackenzie Williams. Preliminary information suggested a homicide followed by a suicide.
The investigation then led police to Mackenzie Williams' home in Issaquah. There, they discovered the bodies of his wife, Harmony Danner, 44, and his younger brother, Dominick. Both had been shot and their deaths were ruled homicides. Authorities believe Mackenzie Williams shot and killed his wife and brother in their Issaquah home before driving to his mother's house on Mercer Island, where he killed her and then himself. The King County Medical Examiner's Office confirmed that Dominick Cuvillier, Danielle Cuvillier, and Harmony Danner all died from gunshot wounds, while Mackenzie Williams died from a self-inflicted gunshot wound.
Court records revealed a bitter and year-long legal battle between Mackenzie Williams and his mother, Danielle Cuvillier, over the care and guardianship of Dominick. Due to his Angelman syndrome, Dominick required significant assistance with daily living. The dispute had escalated over the year, with Danielle having previously filed for a protection order against her son, citing concerns about his mental stability and access to firearms. This had led to Mackenzie surrendering 53 firearms to the Issaquah Police Department. Mackenzie, in turn, had accused his mother of being abusive towards Dominick and had previously contacted Adult Protective Services. The protection order against Mackenzie was dropped just three weeks before the killings. A court had awarded full custody of Dominick to his mother in November 2025, with visitation rights granted to his brother. Friends and neighbors on Mercer Island remembered Dominick for his joyful presence and the special bond he shared with his mother, with whom he was often seen on walks. Community members had even created a tradition of hiding small toys in the trees for him to find. The tragic events have left the community in shock and mourning the loss of what they described as a loving mother and her beautiful son.
