Authorities identify 4 victims, confirm murder-suicide in Mercer Island-Issaquah deaths

Police have identified all four victims — including a mother and son — found dead in homes on Mercer Island and in Issaquah, and determined their manner of death.

The two victims at the Mercer Island home have been identified as 80-year-old Danielle Cuvillier and her son, 45-year-old Mackenzie “Mack” Williams, according to the Mercer Island Police Department (MIPD). An attorney later confirmed to KIRO 7 that Danielle’s other son, 34-year-old Dominick “Nick” Cuvillier, was one of the victims found dead at the home in Issaquah.

Police have now identified the fourth person as 44-year-old Harmony Crystal Danner, whom friends described as a loving physical therapist, according to KIRO 7.

The media outlet reported the King County Medical Examiner’s Office ruled Danielle’s death a homicide caused by multiple gunshot wounds to the head. Mack’s death was ruled a suicide. Both Nick’s and Harmony’s deaths were ruled as homicides caused by multiple gunshot wounds.

Court records detail family turmoil between mother and son

King County court records, provided by Shawn Garrett with KIRO 7, stated that, according to Mack, his mother filed a petition against him on behalf of Nick who was severly disabled, “to keep me away from my brother so that I cannot be a witness to her abuse and mistreatment of him and to prevent me from being able to advocate for my brother.”

Nick, according to Mack’s court records, had a disability known as “Angelman syndrome,” which required him to have nearly constant supervision, as he is not able to live independently without support.

Mack’s father was Nick’s primary caretaker, and Mack’s father and mother agreed to split care for Nick 50/50. However, Mack claimed his mother didn’t always follow through. Mack’s father then died in 2018, leading to Mack and his mother having a shared caretaking arrangement for Nick.

In the court records, Mack claimed his mother did not want someone keeping tabs on her level of care for Nick.

“She does not want someone else monitoring whether she is taking care of Nick or neglecting him, and she certainly doesn’t want anyone to be in a position to know if she is physically or emotionally abusing Nick, which I believe is happening,” Mack stated.

Mack then divulged that his mother had “serious anger issues” and he believed Nick was being physically abused.

Officers find man and woman dead from gunshot wounds in Mercer Island

Mercer Island police were first called around 10:45 a.m. Tuesday to conduct a welfare check at a home on Southeast 46th Street. Police said the check was requested by an attorney representing the homeowner, who reported receiving a concerning email that raised fears for the occupants’ safety.

“They were concerned with the language that was in the email, enough that they wanted us to go and check on the welfare,” Mercer Island Police Commander Jeff Magnen said. “When our officers arrived, they observed one individual that looked like they had trauma, and they forced entry, and that’s when they found the two victims inside the house.”

Magnen said the officers found a man in his 40s and his mother, a woman in her 70s, both dead from gunshot wounds. He also said officers recovered at least three guns from the home, which will undergo ballistics tests.

“The residents on Mercer Island were a mother and son,” Magnen said. “We’re still very, very early in this investigation. We do not see any threat to the public at large. This was contained to our residence, and we want to assure the general public.”

A total of four firearms were recovered at the home, and an additional firearm was found in a vehicle that was impounded as part of the investigation.

Investigators then became concerned about another individual who had previously lived at the Mercer Island home. As a precaution, Issaquah police were asked to conduct a welfare check.

Man and woman also found dead in Issaquah 

Around 11:37 a.m., officers went to a home on Southeast Evans Lane, about a block from Issaquah Middle School. Inside, they found a woman in her mid-40s and a man in his mid-30s dead. Police said there were no signs of forced entry.

“We came up with another address and asked the Issaquah Police Department to do a welfare check,” said Magnen. “When they did so, they reported back to us that they found two deceased individuals inside that residence.”

A neighbor across the street from the Issaquah crime scene, Susan Schroeder, said the discovery was deeply unsettling.

“I mean, it’s hard knowing that they’re right across the street. No one could do anything, I guess,” she told KIRO 7. “It’s just so sad. It’s the holidays, and people are having a tough time.”

Police: There is no threat to the public

Police said there are no outstanding suspects and no threat to the public. It remains unclear which deaths occurred first or exactly how the people in the two homes were connected.

The investigation is ongoing. The King County Medical Examiner’s Office will determine the official cause and manner of death.

“We’re a tight-knit community, we’re a small community, and this type of thing scares the heck out of people,” said Magnen. “We want to assure them, there was no ongoing threat.”

This story was originally published on December 31, 2025. It has been updated and republished since then.

Contributing: KIRO 7; Julia Dallas, MyNorthwest

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