The corrections officer, 56, was treated and released. Investigators believe he was punched in the face during a religious service at an activities building in the Minimum Security Unit. He was knocked backward and struck his head on a door.
The inmate, 59-year-old Allen Pavese, was being held Thursday in segregation, Monroe Correctional Complex spokeswoman Susan Biller said.
Pavese is serving time for a 2008 bank robbery in Moses Lake, according to articles in the Columbia Basin Herald newspaper.
The alleged assault was reported just before 4:30 p.m. Wednesday.
Preliminary police reports said the assault took place outside the chapel where Monroe corrections officer Jayme Biendl was strangled by inmate Byron Scherf in 2011.
Corrections officials on Thursday afternoon clarified the location.
Scherf was convicted of first-degree aggravated murder and sentenced to death earlier this month. The chapel was closed for months after the killing.
Monroe police are investigating Wednesday's incident as a potential case of third-degree assault, spokeswoman Debbie Willis said.
Prison officials also plan an internal review of what happened.
Rikki King: 425-339-3449; firstname.lastname@example.org
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