Detectives investigating the death of a Washington state woman whose body was found buried under a shed discovered a letter at the suspect’s home that described a planned burglary and sexual assault, the Thurston County sheriff said Monday.

The injuries that killed Marcia Norman, 82, included trauma from a pneumatic nailer, Thurston County Coroner Gary Warnock said.

“Her onset from injury to death was not instant. It was hours,” Warnock said. He said the case was the worst he has seen in his career.

Jeffrey Zizz, 47, a handyman who worked for Norman, was booked Sunday on charges of murder, kidnapping and unlawful disposal of human remains. He is expected to be formally charged by Wednesday, Thurston County Prosecuting Attorney Jon Tunheim.

Zizz had a preliminary court appearance Monday and has not yet entered a plea.

He was being held without bail Monday. Online court records did not show an attorney who could speak on his behalf Monday night.

Norman was found April 9 buried under a shed in a shallow grave with concrete poured overtop after cadaver dogs alerted on the property and following the use of ground-penetrating radar, the sheriff’s office said.

Zizz was the last person to see Norman on April 1, and investigators later learned he had dinner with her that night, Sheriff Derek Sanders said.

Norman’s family reported suspicious circumstances regarding a missing person April 4.

Searches the next day at Zizz’s house and room uncovered “a five-page letter which meticulously planned out a burglary and sexual assault of a woman who is referred to as his customer,” Sanders said.

The letter is part of the investigation. Sanders said “there are similarities” in what’s described in the letter and what evidence shows happened in the Norman case, he said.

“That part we’re still investigating,” Sanders said, adding that detectives have a lot of follow-up work to do. “The letter that they uncovered is extremely disturbing.”

There is no evidence of sexual assault, officials said.

A motive in the killing is not clear. “If I had to guess at this point in time, it’s because the suspect that we have in custody is a violent person,” Sanders said.

Officials said Zizz fled to Montana as detectives investigated Norman’s disappearance. Authorities in Thurston County obtained an arrest warrant for a probation violation from a previous child molestation case, officials said.

Zizz was arrested in Missoula, Montana, on April 7 and extradited to Washington on April 13, the sheriff’s office said.

Zizz had been initially interviewed in Norman’s disappearance and his answers seemed reasonable, Sanders said, but a license plate reader in Olympia contradicted his claim he was home the night she disappeared.

“That was the first step in which we were able to put him into a lie and then expand further,” Sanders said.

An arraignment is scheduled for May 6, he said.