The Washington correctional officer found strangled Saturday evening in the chapel sanctuary of a medium-security prison had previously raised concerns about working alone in an area without full coverage from surveillance cameras.

Officer Jayme Lee Biendl, 34, was discovered unresponsive at her duty post in the sanctuary of the Monroe Correctional Complex, and pronounced at 10:50 p.m. Colleagues discovered she had not turned in her keys and radio.

The 5-foot-3-inch, 130-pound Biendl was apparently strangled by Byron Scherf, a "three strikes" lifer with a criminal past that included two convictions for violent attacks on women. Sherf, 52, weighs about 200 pounds.

On Monday, the state's top correctional official told POLICE Magazine the agency was well aware of Sherf's violent past and allowed him additional access privileges, because he had shown good behavior. It was one reason Sherf was transferred to the medium-security Monroe facility.

"He showed us no rule violations in the past 10 years," said Eldon Vail, secretary of the Department of Corrections. "He kept to himself. He wasn't giving us any trouble … Until Saturday night, he was a well-behaved, keep-to-himself kind of guy."

The correctional facility in Monroe, built in 1910, houses 2,400 male inmates who are mostly violent offenders, Vail said. Correctional officials are now investigating the attack on Officer Biendl, who was named officer of the year in 2008.

Several years ago, Officer Biendl had identified an inmate who concerned her, and the facility removed the inmate. So far, the facility hasn't found documentation about concerns regarding Sherf, Vail said.

"He was a frequent visitor to the chapel, so I'm sure he knew who she was, and she knew who he was," added Vail.

Union officials say the correctional officer had raised frequent concerns about working alone in the sanctuary to her supervisors.

"She was feeling unsafe about this because she's off in the chapel and oftentimes supervising lots of inmates, and she had let her supervisors know that she was not feeling safe," Tracey Thompson, secretary-treasurer for the state corrections officers union, Teamsters Local 117, tells the Seattle Times . "My understanding is there were repeated complaints."

The prison doesn't provide a sidearm or TASER to officers working inside Monroe, because the weapons could be taken away and used against them, Vail said.

"It's not generally done," Vail said. "That equipment is available, and we're not afraid to use it when we need to, but generally we don't have to."

Sherf is a twice-convicted rapist who served 12 years starting in the late 1970s for raping a young waitress, dousing her with gasoline and setting her on fire. She lived to testify against him.

Two years after his release in 1993, Sherf abducted and raped a Spokane real-estate agent who reported him to police. Sherf was ultimately sentenced to life in prison without the possibility of parole.