WINTHROP — A man suspected of killing a nationally known dog trainer last week was initially captured and detained in Okanogan County while Skagit County authorities pieced together evidence.

T. Mark Stover, 57, a dog trainer whose clients have included the Mariner’s Ichiro Suzuki and Starbucks founder Howard Schultz, is missing and presumed slain, according to the Skagit County Sheriff’s Office.

His ex-wife’s boyfriend — Michiel Glen Oakes, 41, of Kennewick, was at a Winthrop-area residence on Oct. 29 when authorities discovered evidence they say links Oakes to Stover’s disappearance the day before. According to the Skagit County Sheriff’s Office, Stover, who ran Island K-9 Training from his home near Anacortes, was last seen by his employees before 9 a.m. Oct. 28.

Oakes is being held in Skagit County Jail on $5 million bail in connection with the slaying.

His girlfriend and Stover’s ex-wife, Linda Opdycke, called Okanogan County Sheriff’s Office from her home near Winthrop on Oct. 29, after she heard her ex-husband was missing.

Okanogan County Sheriff Frank Rogers said she had apparently had problems with Stover before, and was worried he was heading to Winthrop.

Rogers said his Chief Criminal Deputy Dave Rodrigez and Deputy Gene Davis went to her home. When they arrived, Oakes was at the residence with her, he said. While they were there, he went out to his vehicle to get some medications, and they saw him retrieve a white plastic bag from the car and throw it over a bank. An affidavit filed with his charges states that it contained a .22-caliber semi-automatic pistol.

Rogers said the officers detained Oakes after Skagit County discovered new information tying Oakes to the disappearance, and later transported him to the Skagit County line. He said they also impounded his vehicle until Skagit County received a search warrant, and came to Okanogan County to retrieve it.

According to an affidavit filed by the Sheriff’s Office, the first clues in the case were gathered Oct. 28, while Stover was thought to be seeing clients in Seattle.

According to the affidavit, a woman called the Skagit County Sheriff’s Office shortly before noon to report that two vehicles were illegally parked at the Summit Park Grange, a half-mile from Stover’s house. The two cars were parked back to back in an area of the grange that had been closed off with a locked chain, the woman told police.

She also said there was clear plastic stretched between the two vehicles, police said.

The woman got the license-plate numbers, and the cars turned out to be registered to Stover and Oakes.

Oakes’ car was gone by the time a deputy responded, but Stover’s unoccupied station wagon was still there. The car remained there when the deputy left.

The deputy stopped Oakes a short time later, the affidavit says. Oakes said he was lost and denied having been behind the grange, according to police.

He was let off with a warning, but the deputy noticed, according to the affidavit, that the back of the car appeared to be “full of blankets or sleeping bags.”

Deputies were called to Stover’s residence in the 13100 block of Thompson Road on Oct. 29, when his employees arrived to find Stover’s dog was wounded and bloody. The dog survived.

Deputies found what appeared to be blood stains on the front porch and in the house.

They also noted the bathroom was unusually clean and smelled like “fresh bleach,” according to the affidavit.

A few hours later, Stover’s station wagon was found abandoned in the parking lot of the Northern Lights Casino, on the Swinomish Indian Reservation, about three miles from the grange. Police found what appeared to be bloody fingerprint smears in the station wagon.

Police have been searching the Swinomish Channel, which separates Fidalgo Island from the mainland, for Stover’s body after a cadaver dog last week indicated a body may have been in the area.

World staff writer K.C. Mehaffey contributed to this report.