The fire broke out about 2 a.m. Wednesday at a house in the 13200 block of 240th Street NE in the Arlington Heights area, said Branden Bates, assistant fire chief at Snohomish County Fire District 21. No injuries were reported.
The fire was at the same address where David Thorsen, 50, lived until his arrest in June, police confirmed.
Investigators with the Snohomish County Fire Marshal's Office remained at the scene as of noon Wednesday. It likely will take some time to determine the cause of the fire, they said. Crews also were working on hot spots.
Snohomish County sheriff's major crimes detectives were notified and were waiting on the fire investigators' reports, sheriff's spokeswoman Shari Ireton said.
In June, David Thorsen's mother, Betty E. Thorsen, 80, died after an apparent fall. Her exact cause of death remains under investigation by the Snohomish County Medical Examiner's Office.
Hours later, police returned to the home and found the body of David Thorsen's sister, Karen Harris, 53, under a blanket in a field nearby. Police allege that he killed Harris and then used a riding lawn mower to move her body.
Detectives also have been looking at the April 11 death of the suspect's father. The King County medical examiner earlier ruled Jack Thorsen's death an accident from "a presumed fall." He was 84.
David Thorsen is being held at the Snohomish County Jail on $1 million bail.
Rikki King: 425-339-3449, email@example.com.
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