Officials identified a mother and her adult son in Mercer Island; two relatives found dead in Issaquah remain under review by the medical examiner.
MERCER ISLAND, WA — Police on Wednesday identified a woman and her son found shot to death during a welfare check at a Mercer Island home, and said two additional relatives discovered hours later in Issaquah were part of the same case. Investigators said the sequence appears to be a homicide followed by a suicide, with no ongoing threat to the public.
Authorities named the Mercer Island victims as Danielle Cuvillier, 80, and her son, Mackenzie “Mack” P. Williams, 45. Detectives said the deaths are tied to two more people found dead at a residence in Issaquah late Tuesday morning. The King County Medical Examiner is working to confirm identities, causes and manners of death for the Issaquah pair. Police from both cities, along with county investigators, say the case remains active as they review evidence from the two homes and trace the family connections that led officers from one address to the next.
According to police, officers were sent to the 8400 block of Southeast 46th Street around 10:45 a.m. Tuesday after an attorney for the homeowner reported receiving an alarming email and asked for a welfare check. When officers looked through a window, they saw a person who appeared to have a gunshot wound. After forcing entry, they found Cuvillier and Williams dead inside, with firearms located near the bodies. “Both were found with obvious gunshot wounds,” Commander Jeff Magnan of the Mercer Island Police Department said, adding that preliminary information points to a homicide followed by a suicide. Detectives collected several firearms in the house and an additional gun from a vehicle outside, police said.
As Mercer Island detectives processed that scene, they developed concern for another family member who had previously lived at the home, according to police. Around 11:37 a.m., Issaquah officers conducted a welfare check at a residence in the 400 block of Southeast Evans Lane and found a woman in her mid-40s and a man in his mid-30s dead inside. There were no signs of forced entry, and investigators said evidence indicates there are no outstanding suspects. Officials said the Issaquah home is connected to the Mercer Island case through family ties, though they have not publicly detailed the order of the deaths or the specific relationships beyond that link. The medical examiner will determine the official cause and manner in all four deaths.
Records reviewed by reporters show the family had been involved in a drawn-out court dispute over caregiving and decision-making for a younger adult son with significant disabilities. Court filings over the past year describe tense encounters at the Mercer Island home, competing guardianship claims, and temporary protection orders that at one point included the surrender of dozens of firearms. In statements to local media, an attorney for the family confirmed the Mercer Island victims’ names and said relatives were in shock and asked for privacy as they grieved. Police have not linked the legal dispute to the shootings and said the motive remains unknown.
Neighbors in both cities described a quiet Tuesday morning interrupted by flashing lights and crime-scene tape. On Mercer Island, patrol cars blocked off Southeast 46th Street for hours as detectives photographed the single-story home and canvassed for surveillance video. In Issaquah, residents on Southeast Evans Lane said officers announced themselves, forced entry and then cordoned off the small cul-de-sac. “They were always kind, considerate neighbors,” said Shelby Rosales, who lives near the Issaquah address. “But people have lives that we don’t know about.” Investigators said they recovered multiple firearms and are running traces while they wait for ballistics and autopsy findings.
Police said there is no wider public safety concern stemming from the case. Mercer Island officials emphasized that the email requesting the welfare check allowed officers to respond quickly and begin coordinating with Issaquah police. Detectives are now reconstructing a timeline spanning the two addresses, including when each person was last seen alive and when the concerning message was sent. Forensic teams are analyzing electronic devices, doorbell cameras and shell casings, while detectives are interviewing relatives, friends and caregivers who interacted with the family in recent weeks.
Officials have not released detailed information about the guns involved, how many shots were fired, or which of the deaths occurred first. Police said they do not believe any other people were present in either home at the time of the shootings. The residences themselves were not ransacked, and neither scene showed signs of forced entry, according to statements from both departments. Detectives are also reviewing prior welfare calls and adult protective services contacts, if any, involving the family to understand any patterns that could inform the sequence of events.
The King County Medical Examiner’s Office will complete autopsies and issue formal determinations for each death. Once that work is finished, police expect to release a more detailed chronology of what happened at the Mercer Island home and later at the Issaquah address. Investigators said any final case findings will be forwarded to prosecutors for review, a standard step even when the suspected shooter is among the dead. Both departments said further public updates will come after next of kin notifications and medical examiner identifications for the Issaquah victims are complete.
On Wednesday evening, flowers and candles appeared near the curb outside the Mercer Island home. A neighbor paused to straighten a small bouquet and read a handwritten note tucked beneath it. “It’s heartbreaking,” said a man who lives a few houses away, declining to give his name. “We woke up to police everywhere, and then we learned a family was gone.” Across town in Issaquah, a neighbor described quiet visits by detectives to several houses on the block as they sought doorbell video and asked what residents heard. “We just hope the families get answers,” said another neighbor, standing behind the yellow tape that still lined the sidewalk.
As of late Wednesday, police had closed the Mercer Island scene and were continuing evidence work at the Issaquah home. The medical examiner’s office said it would release the Issaquah victims’ names after formal identification. Investigators plan to share their next update once autopsy results and lab work are back.
Author note: Last updated 2026-01-02.