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Court docs shed light on legal drama surrounding Mercer Island murder-suicide investigation
Court documents now paint a clearer picture of the family legal battle that surrounded four people killed in two cities that were just miles apart. A mom and her son were found dead at a home on Mercer Island on Tuesday, according to Mercer Island Police. That same day, two others were also found dead at an Issaquah house.
MERCER ISLAND, Wash. - Court documents reveal a family guardianship dispute was underway before the deaths of four family members found in homes in Issaquah and Mercer Island on Tuesday.
The search for answers continued Wednesday into their deaths, though Mercer Island police have said it appeared to be a murder-suicide carried out between two homes, miles apart.
Police were still on the scene at the Issaquah home Wednesday night.
What they're saying:
"We never heard anything," said Yana Babich, an Issaquah neighbor.
Neighbors in Issaquah and on Mercer Island were still coming to terms with what happened the day before New Year's Eve.
"We are all in shock. I can't believe it really happened," Babich said.
Legal battle over disabled son preceded Mercer Island, WA, murder-suicide
Court records show a heated guardianship battle over a disabled son preceded the deaths of four family members in two cities just miles apart.
The backstory:
Police say they first found Danielle Cuilliver and her older son at her Mercer Island home on Wembley Lane after a family attorney called for a welfare check. That residence is pictured below.
When officers arrived, they could see someone on the floor who appeared to have been shot. When they went inside, they found Danielle Cuilliver deceased, along with her middle-aged son, Mackenzie "Mack" Williams.
Four guns were also found in the home, and a fifth was found in a vehicle, according to Mercer Island police.
Neighbors say that though Danielle was older, she was vibrant and helped tend to the community pool. She liked yoga and was often seen walking her dog in the neighborhood around her Mercer Island home.
"A little scary having something like that happen," said Frank Ceteznik, Danielle's neighbor. "Just met her a few times, but really nice lady."
Dig deeper:
Meantime, police say two other family members, a man and a woman, were also found at a home in Issaquah. Court documents from the guardianship dispute indicate that Danielle's older Mackenzie "Mack" Williams, had listed it as his home address.
"It's unbelievable, unbelievable. Who knew it could happen here?" said Babich, who was a neighbor of Mack Williams.
King County court documents also show that the guardianship dispute brewing between Danielle and her older son, Mack Williams, began in early 2025.
The two were at odds in court over the guardianship of Danielle's younger son, Dominick, a man in his 30s who friends say was known as "Nick".
Court records state Nick "has Angelman's syndrome and has significant developmental delays."
Nick is also Mack's younger brother.
Documents show that Danielle had filed a petition for guardianship of her younger son, Nick, and it was granted by the court in November.
Danielle's attorney argued in court that Nick "was removed from his home by his brother, Mack Williams, in early 2025. Mack was then accused of influencing Nick "to execute a new power of attorney, naming (Mack) Williams as his agent."
Court documents show that while Danielle had recently won full-time guardianship of her younger son, Nick, her older son, Mack, was allowed visitation.
What's next:
Police have not yet released information on a possible motive for the killings.
Neighbors say it is a tragic situation for all involved.
"It just really feels sad that this has happened, sad for everyone," said Ceteznik.
FOX 13 reached out to the attorney listed in the guardianship dispute for Danielle and is waiting to hear back.
The Source: Information in this story comes from original reporting by FOX 13 Seattle.
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