Kevin A. Bradfield made the claim in a letter he sent to a family member in Oregon, according to a supplemental statement of probable cause filed in the case. Investigators managed to intercept the letter sent from the Clallam County Jail.
Bradfield has been charged with second-degree murder in Pimentel's death. His girlfriend, Kendell K. Huether, has been charged with rendering criminal assistance. Both were longtime friends of the murder victim.
Pimentel, who functioned at the level of a 12-year-old, was just 27 when she was murdered in October 2011. Her body was found dumped in a wooded area near the Hood Canal Bridge.
The two suspects initially claimed Pimentel had accidentally fallen down some steps in the home and died from a broken neck. They said they panicked and decided to fabricate a story about Pimentel having run off with an unknown man.
But upon further questioning, Bradfield later admitted to having strangled Pimentel, who reportedly yelled, "Stop, you're killing me. Please stop!" and "Kendell, help me!" during the attack.
After Pimentel went limp, Huether said she watched Bradfield pick up Pimentel's upper body and drop her back down as he said, "Look, I killed her," court documents said.
Bradfield also told detectives that he and Huether wrapped Pimentel in a blanket, wheeled her to a van in a shopping cart, then drove into Jefferson County to dispose of her body, taking Huether's children with them.
They covered the body with soil and loose vegetation, they said, and scattered the contents of her purse along Highway 101 as they drove back to Port Angeles.
Both suspects have been booked into the Clallam County Jail pending their trials. If convicted, Bradfield could face life in prison. Huether, however, may receive 11 months as a result of a plea deal in the works.