The bodies of a missing Salem woman and her son were found Saturday in a wooded and remote area of Yamhill County, authorities say.

Police have been searching for Karissa Fretwell, 25, and her son Billy Fretwell, 3, since May 17, when a family member discovered their apartment unlocked, the television on inside, and Karissa Fretwell’s bank card and glasses – items she would normally never go without – left behind.

The investigation led police to an area about 10 miles west of the city of Yamhill, where members of multiple police and rescue agencies searched for two hours Saturday before finding the bodies.

The state medical examiner determined in an autopsy Sunday that Karissa Fretwell died of a single gunshot to the head and ruled the death a homicide. Billy Fretwell’s cause and manner of death has not been determined, authorities said.

The Yamhill County Sheriff’s Office and district attorney declined to add additional details regarding the search and discovery.

Salem police and Yamhill County prosecutors had already arrested 52-year-old Michael John Wolfe, Billy Fretwell’s father, in connection with their deaths. He was charged with aggravated murder and kidnapping but denied involvement in their disappearance in interviews with police.

Wolfe and Karissa Fretwell had recently gone to court in a child support dispute. Court records show that Wolfe was ordered in April to pay over $900 a month in child support. Fretwell had sole custody of her son, and the two had been living in West Salem.

Billy Fretwell’s babysitter told police Karissa Fretwell reported being threatened by Wolfe and his wife, who said they would take custody of the boy.

Detectives obtained data from Karissa Fretwell’s cellphone showing her phone sent a text message the day after friends and co-workers report she was last seen. The phone used a cell tower southeast of Gaston, which provides coverage to Wolfe’s rural property.

Authorities also received cell data placing Karissa Fretwell’s phone near Wolfe’s place of work, a steel mill in McMinnville. He told police he was working at the mill the night of May 13 and morning of May 14, but detectives believe surveillance video and cell tower activity disputes that.

Footage at the mill shows Wolfe leaving his work area on a golf cart and walking toward a line of trees and bushes to a nearby parking lot. A police affidavit describes that behavior as “outside of protocol."

Wolfe reappears through the trees almost five hours later, the affidavit states, and drives the golf cart back to his work area while carrying a white trash bag filled with unknown items.

Phone records from May 13 also show Wolfe’s phone pinged cell towers “away from his place of work” shortly after he disappeared through the trees. That evening, Wolfe’s phone pinged a tower that would cover Fretwell’s apartment in Salem and pinged towers near his workplace about the time he reappeared at his workplace. Wolfe told detectives he had not been to Salem in more than a year.

-- The Oregonian/OregonLive