Nearby Cowlitz County was investigating the Tuesday afternoon death, with the assistance of that county's coroner, said Dan Bigelow, Wahkiakum County prosecutor and coroner.
Dearmore's deputies had gone to his home after the sheriff's wife reported that he was making suicidal statements, Cowlitz County Sheriff Mark Nelson said in a statement.
The deputies, both friends of Dearmore, had entered the door to the workshop where Dearmore was when he shot himself, Nelson said.
Nelson said it appeared Dearmore may have been depressed over ongoing medical issues stemming from an old work-related injury.
Dearmore had been sheriff for two years and involved in law enforcement for 25 years, Wahkiakum County spokeswoman Marsha LaFarge said.
"Nobody saw this one coming," said Rick Nelson, publisher of the Wahkiakum County Eagle newspaper. "Just about everybody I know really liked and respected Jon."
Undersheriff Mark Howie will run the sheriff's office in the interim, The Daily News of Longview reported.
"I'm very shocked," County Commissioner Dan Cothren told the newspaper. "I'm trying to absorb what has happened."
The Wahkiakum County sheriff's office has five full-time deputies, a small support staff and a handful of reserves. Nelson said Howie had asked for assistance and that Cowlitz County would patrol eastern Wahkiakum County, while the Pacific County sheriff office would patrol the west end. Wahkiakum County lies along the Columbia River.
"This is tragic for any agency, but for one the size of Wahkiakum County sheriff's office, it's devastating," said Nelson.
Dearmore, 50, worked as a bank branch supervisor in Chelan before he went into law enforcement, according to a 2010 interview with the Longview paper. He grew up loving "Gunsmoke" and other TV westerns, and as a youngster imagined himself as a frontier lawman, he said.
He entered a six-month police reserve academy in his mid-20s. After a day of working at the bank, he would head to the Chelan police station and hop in a cruiser to shadow the first officer he could find, he told The Daily News.
"I got bit by the bug," he said.
Dear is survived by his wife and a daughter.
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