The four people who died in a suspected homicide-suicide in Mercer Island and Issaquah homes were related, Mercer Island and Issaquah police said.
Danielle Cuvillier, 80, and her son, Mackenzie P. Williams, 45, were found dead Tuesday morning at a Mercer Island home in the 8400 block of Southeast 46th Street. Later in the day, a second adult son and a woman in her 40s were found dead in an Issaquah house in the 400 block of Southeast Evans Lane, where police were doing a welfare check.
The Mercer Island Police Department identified Cuvillier and Williams on Wednesday afternoon. The other two have not been publicly identified.
The Mercer Island deaths are being investigated as a homicide and suicide, police Cmdr. Jeff Magnan said. It is unclear who shot the other before turning the gun on themself.
After Mercer Island police responded to the deaths of Cuvillier and Williams, they asked Issaquah police to do a welfare check on the woman's other son, who was in his 30s, in Issaquah, Magnan said Wednesday. The son was found dead along with a woman in her 40s. The woman and one of the sons were married, according to Issaquah police.
The two people in Issaquah had been shot and killed, and there were no signs of forced entry.
Four firearms were found inside the Mercer Island home, which was owned by the mother, and a fifth firearm was found in a car. The two addresses are about 14 miles apart.
The King County medical examiner’s office will determine the cause and manner of the deaths.
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