Artist, 80, and her two sons among four killed in triple murder-suicide in upscale Seattle suburb

An 80-year-old artist, her two sons, and her daughter-in-law were all found dead early Tuesday morning in a suspected triple murder-suicide that was carried out at a pair of homes in swanky Seattle suburbs.

Danielle Cuvillier, 80, and her son, Mackenzie P. Williams, 45, were found dead Tuesday morning at a home in Mercer Island, just seven miles outside of Seattle, local cops said in a post on Facebook.

Hours later, a woman in her 40s and a man in his mid-30s were found dead in a house in Issaquah, 17 miles outside of Seattle, while police were doing a welfare check, according to a Facebook post from the Issaquah Police Department.

Mercer Island Police Department Commander Jeff Magnan later confirmed that his office flagged Danielle and Williams’ deaths to the Issaquah police and asked them to do a welfare check on Danielle’s 34-year-old son, Dominick Cuvillier, and Williams’ wife, the Seattle Times and KIRO 7 reported.

Danielle’s attorney told KIRO 7 that Dominick was one of the victims found at the Issaquah home. Neighbors also confirmed with the outlet that Williams’ wife was the second unidentified victim.

Danielle and Williams’ deaths are being investigated as a homicide and suicide, though police haven’t identified the shooter.

The mother was a “dedicated artist” with an interest in photography, sharing her work on Instagram over the years.

Authorities recovered four firearms inside the Mercer Island home and found a fifth in a car on site, according to the Mercer Island Police Department.

The Issaquah deaths are being investigated as homicides, according to KOMO News. Authorities noted that both victims had been shot, and there was no sign of forced entry.

The gruesome deaths came after more than a year of intense conflict between Danielle and Williams about the artist’s younger son’s care, according to court documents obtained by the outlets.

The 34-year-old was diagnosed with Angelman syndrome, a rare genetic disorder that causes severe developmental delays and requires extensive round-the-clock care.

Dominick lived with his parents until his father died in 2018. After that, Williams stepped in and arranged a shared caregiving regimen for him with their mother.

Williams accused Danielle of physically and emotionally abusing his disabled brother in a King County court declaration, which Danielle denied, the outlets reported.

In January 2025, Williams met with a lawyer and started working towards assuming power of attorney, with his brother’s consent, so he could be solely responsible for his sibling’s care.

Danielle then accused her younger son of being “unduly influenced” to relinquish control to Williams, the Seattle Times reported.

The matriarch was later charged with fourth-degree assault after a tiff with Williams at the Mercer Island home, which she refused to let him enter.

Danielle later filed a petition for a protection order against Williams on behalf of her younger son. In the order, she claimed Williams’ “behavior has been unpredictable and aggressive lately” and highlighted the startling number of firearms in his home, the outlet reported.

Williams confessed to having 53 firearms in his home, which he surrendered, according to a separate document.

The protection order was approved and reissued three more times, but was terminated in early December.

In August, Danielle and Williams agreed to have Dominick live with his mother, but permitted visitations on Sundays and Mondays, plus one weekend a month. They agreed to only communicate with each other over text and email so that Dominick wouldn’t be caught between their squabbles.

Danielle was also named as his sole guardian and conservator.

The King County medical examiner’s office will determine the cause and manner of all the victims’ deaths.