Police found the body of Dustin W. Gilman, 22, on Monday morning in the Wandermere area north of Spokane. The medical examiner identified the body.
Authorities did not say how Gilman died.
He was wanted in connection with Friday's slayings of Tracy Ann Ader, 32, and her 8- and 10-year-old sons at their home, where Gilman had been staying as a family friend. Ader's husband was in the hospital at the time with an unrelated illness.
A makeshift memorial has been set up outside the family's Spokane home.
"They were just the sweetest boys ever," Melody Ponsness, Ader's cousin, told The Spokesman-Review newspaper. "They always gave you a hug before you had to go back home. It's hard to find words. It's just so shocking."
Gilman spent nine months in prison in 2009 after he was convicted of two counts of second-degree trafficking in stolen property. The Aders had befriended him and he had moved in with the family, officials have said.
Police found the slain family's 2007 Nissan Pathfinder in a convenience store parking lot in Spokane on Sunday. A police dog was unable to pick up the suspect's trail.
Gilman's father, Larry Gilman, on Saturday told police that he had spoken to his son on the phone and heard a shot, which made the elder Gilman believe that his son had committed suicide.
Dustin Gilman had been living with the Aders for several months. He watched over the two boys and attended family gatherings.
Police believe Gilman is still in Spokane, and describe him as armed and dangerous. However, alerts have been sent via the National Crime Information Center to all 49 other states. Border agents are also on the lookout for Gilman, who is described as 5-foot-8, 170 pounds, with blond hair and blue eyes.
Several weapons were taken from the house where Ader and her children were found.
