Detectives arrested a Gaston man Friday, charging him with two counts of aggravated murder in the case of a missing Salem mother and her young son.

Michael John Wolfe, 52 — the boy's biological father — also faces two kidnapping charges, according to Salem police.

Multiple agencies continued searching Friday for Karissa Fretwell, 25, and her son, William, 3. The pair was last seen May 13; their last known location was West Salem.

The two were reported missing May 17 by family after Fretwell didn't show up at work.

Wolfe, who lives on rural acreage in Yamhill County, had been identified earlier as a person of interest in the case, prompting searches of at least two properties.

At a press conference Friday, Salem police Lt. Treven Upkes said detectives found him at a doughnut shop in Portland — Blue Star Donuts at 12th and Morrison streets.

Upkes declined to provide many details on the case — including why Wolfe was a suspect in the case — due to the ongoing investigation. Wolfe was booked into Yamhill County Jail and is being held there without bail.

Upkes said officials can have probable cause for an arrest even if they don't have every fact in place when an arrest is made, knowing that more investigative work could still take place. Charges also can change at the district attorney's discretion based on additional evidence, he said.

"Based on what we have at this point, we believe that we can charge him with aggravated murder and kidnap," Upkes said.

However, investigators "are dogged in their pursuit of finding William and Karissa," Upkes said.

Wolfe was being booked in Yamhill County because that's where authorities believe crimes took place, he said. Wolfe is expected to be arraigned at 1:30 p.m. Tuesday, May 28.

A DNA test established Wolfe was William's biological father, according to a Polk County court judgment. Fretwell in 2018 filed a petition to establish paternity of William, and she had full custody.

Authorities searched a home near Gaston and a field on Hopewell Road northwest of Salem just across the Polk County line, according to Salem police.

On Friday, Clackamas County Sheriff's Office divers assisted Salem police and other agencies in the search, according to the sheriff's office.

In Gaston, the search was on a property on NW Phillips Road. Court records list Wolfe's address as being on 2700 NW Phillips Road.

Randy Ruggles, a neighbor of Wolfe's in Gaston, said Wolfe and his family have lived at the estimated 10-acre property for about eight years.

"This was a big shocker to us," Ruggles said Thursday. "It's just scary."

Law enforcement officials from the FBI and Salem Police have been at Wolfe's house since Sunday, he added.

Ruggles said the last time he saw Wolfe was months ago.

"We don't mingle," he said of his neighbors on NW Phillips Road. "Everyone works and keeps to themselves."

Karissa is described as 5 feet 9 inches tall, weighing approximately 135 pounds. She has blue eyes and naturally blond hair that she dyes red.

William is a white male, approximately 3 feet tall, and weighs approximately 30 pounds. He has blond hair and blue eyes.

Fretwell's friend Megan Harper, of McMinnville, said she was supposed to watch William on May 17, but never heard from Fretwell. The last time they spoke was May 11 when Fretwell asked Harper about installing Ring, a security camera system.

"I feel ill with worry about William," Harper said.

Harper described Fretwell as "shy and awkward" when they first met in a sociology class at Chemeketa Community College.

Jonathan Bach has been a reporter with the Statesman Journal since 2016. Contact him by email at jbach@statesmanjournal.com, call (503) 399-6714 or follow him on Twitter @jonathanmbach