Tony Clyde Reed, 49, was taken into custody by the US Marshals Service and has been booked into the San Diego County Jail.

He arranged with officials to turn himself in. Tony Reed's brother and the second suspect in the slayings, John Blaine Reed, is still outstanding.

Both Tony and John, 53, fled to Mexico via Ellensburg after the killings, according to officials.

The bodies of Patrick Shunn and his wife, Monique Patenaude, still have not been found.

>> Read more trending stories

Investigators hiked to where the missing couple’s Land Rover and Jeep were found in a wooded area near Oso, Washington.

After looking through their abandoned cars, Snohomish County Sheriff's officials say they found evidence of a slaying and incriminating evidence in a home where John Reed once lived. Detectives said they were also able to obtain video surveillance footage tying the Reed brothers to the disposal of the vehicles.

“John Reed’s former house was very close to where Patrick and Monique lived,” said Snohomish County Sheriff Ty Trenary.

Detectives have acknowledged that there were property disputes between the Reed brothers and the missing couple.

Shunn and Patenaude owned a large lot near the Stillaguamish River. They filed a lawsuit against the Reeds three years ago, claiming the brothers drove their RVs onto their property and let their dogs harass their farm animals.

When the couple didn't come home, their neighbors took notice.

“So everybody’s kind of up in arms, keeping track of each other and calling concerned when people are not answering phones, so it’s a concern," neighbor Damon Davis said.

Meanwhile, detectives confirmed that the Reed brothers were in possession of their parents’ red 2007 Volkswagen EOS Coupe, with Washington license AXH5106.

John Reed, 53, was described as around 5 feet 8 inches tall, 190 pounds with hazel eyes and gray hair.

"The public should absolutely be worried," Trenary said.

Anyone with information on the whereabouts of John Reed or with information about the investigation into the murder of Shunn and Patenaude is asked to call 911 or the Snohomish County Sheriff's Office anonymous tipline at 425-388-3845.