Mom, 2 Sons and Daughter-in-Law Found Dead in Suspected Murder-Suicide By Becca Longmire

A mother, her two sons and her daughter-in-law have been found dead in a suspected murder-suicide near Seattle, according to multiple reports.

On Tuesday, Dec. 30 at approximately 10:45 a.m. local time, Mercer Island Police Department (MIPD) officers “were dispatched to a residence in the 8400 block of SE 46th Street to conduct a welfare check,” a news release shared on Facebook stated.

“The request originated from an attorney representing the homeowner, who reported receiving a concerning email that raised fears for the occupants’ safety,” the police post noted.

It continued, “Upon arrival, officers looked through a window and observed an individual inside the residence who appeared to have suffered a gunshot wound,” adding, “Officers made entry into the home and located two deceased individuals … Firearms were found within the residence and in proximity to the individuals.”

The MIPD later identified the two deceased in the Mercer Island home as Danielle Cuvillier, 80, and her son, Mackenzie P. Williams, 45.

“Based on preliminary information, the incident appears to be a homicide followed by a suicide. There is no indication of an ongoing threat to the community,” MIPD said. 

Out of “concern for another individual” who had also lived at that address, investigators from MIPD asked the nearby Issaquah Police Department (IPD) to check on another residence of the family’s in Issaquah.

There, “in the 400 block of SE Evans Lane,” the IPD found two other deceased individuals, “a female in her mid-40’s and a male in his mid-30’s,” the department confirmed on Facebook.

“There was no sign of forced entry. At this point in the investigation details lead us to believe there are no outstanding suspects and no ongoing threat to the community. These are the only details able to be released at this time.”

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It has since been reported that the deceased are all related, according to The Seattle Times, King 5 Seattle and Fox 13 Seattle.

The Seattle Times stated that Cuvillier’s youngest son had been found dead in the Issaquah home. The woman in her 40’s who was discovered deceased in the property had been married to one of the sons, the outlet reported, citing Issaquah police.

The Issaquah home belonged to Williams and his wife, per King 5 Seattle.

The MIPD said in a Dec. 31 update that they recovered four firearms from the Mercer Island home, along with an additional firearm from a vehicle. “Investigators continue to work closely with the King County Medical Examiner’s Office to determine the official cause and manner of death.”

The deaths reportedly come following over a year of conflict between Cuvillier and Williams amid a dispute over the younger son’s care, The Seattle Times said, citing court documents.

Cuvillier’s youngest son, age 34, had been diagnosed with the rare genetic disorder, Angelman syndrome, which causes severe developmental delays, the outlet stated, adding that he needed 24-hour care.

Williams had reportedly accused his mother of being physically and emotionally abusive, allegations that she denied, The Seattle Times noted, citing a King County court declaration.

Cuvillier was granted guardianship of her younger son in November after filing a petition, Fox 13 Seattle reported, citing court documents. Williams was then accused of encouraging his younger brother to give him power of attorney instead of their mother, the outlet stated.

Williams had reportedly attempted to visit his brother at the Mercer Island home in recent weeks, but Cuvillier would not let him in, leading Williams to call 911, according to The Seattle Times. Cuvillier was charged with fourth-degree assault in Mercer Island Municipal Court after the pair fought, the outlet stated.

Cuvillier then filed a petition for a protection order against Williams on behalf of her younger son, stating that Williams’ “behavior [had] been unpredictable and aggressive lately,” the outlet reported. She also allegedly voiced her concern over the number of firearms her eldest son had in his home.

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The Issaquah Police Department, the Mercer Island Police Department, the Mercer Island Municipal Court, the King County Courts and the King County Medical Examiner’s Office didn’t immediately respond when contacted by PEOPLE for additional information.