Three suspects were arrested Wednesday in Oregon on suspicion of murdering a Tantric massage therapist on a Marin County hiking trail, after the stolen car they were driving was tracked using GPS technology, county sheriff’s investigators said.

The killing of 67-year-old Steve Carter, who was shot to death Monday on Old Railroad Grade Road in the Loma Alta Open Space Preserve northwest of Fairfax, led to a multistate search for the killers and the victim’s Volkswagen Jetta station wagon.

The car was stolen from a parking lot near the trail. On Wednesday, it and the suspects were found in Portland.

Marin County sheriff’s Lt. Doug Pittman said investigators had tracked the station wagon using GPS technology embedded in the car and alerted the Portland Police Bureau.

Two men and a woman — Morrison Haze Lampley, 23, Sean Michael Angold, 24, and Lila Scott Allgood, 18 — were arrested without incident at 2:15 p.m. Wednesday as they ate at a Portland restaurant, police said. Police did not know their home towns.

Pittman did say, “We know these are the same three subjects who were identified early in our investigation” after citizens reported three people who were “acting strangely and seemed out of place.”

The motive for Carter’s killing is unknown, he said.

Pittman said detectives were helped by witnesses and a trail of evidence, including photographs and videos taken at a Marin County convenience store, school and gas station. He showed one photograph taken at a gas station in Point Reyes Station, shortly after Carter is believed to have been shot. It showed the three suspects with the stolen Volkswagen.

“It puts them in possession of the victim’s vehicle,” Pittman said.

Investigators had released images and video Tuesday night of a man and a woman whom police called “persons of interest.” Photographs of a third person, a man wearing a black ski cap and holding a skateboard, were released Wednesday. The three people, who were wearing small backpacks and camping-type gear, were seen near the site of the slaying, authorities said. They were identified as Lampley, Angold and Allgood.

Investigators obtained the video and still photos from a store clerk at a nearby 7-Eleven store on Sir Francis Drake Boulevard.

Carter had recently returned to the United States from Costa Rica to help care for his wife, who is receiving treatment at the Marin Cancer Clinic.

He was staying with friends when he took his Doberman pinscher for a walk Monday evening and encountered his killer on the trail. He was found still clutching the leash to the dog, which had been shot but is expected to survive.

His wife made an impassioned plea for help Wednesday. Lokita Carter was diagnosed with a rare and aggressive form of breast cancer in July, just months after she and her husband sold their Tantric massage and teaching business in the Lake County town of Middletown and moved to Costa Rica to “live a simpler life.”

She is now mourning her husband while enduring cancer treatments that are expected to cost roughly $45,000. As of Wednesday, her online fundraising page had raised more than $25,700.

“The devastating news is that my beloved husband of 17 years, Steve, was murdered in cold blood ... while walking our dog on a popular hiking trail,” Lokita Carter wrote on the online fundraising page.

“I am beyond devastated to face this situation while already going through intensive breast cancer treatment. His senseless and shocking death is incomprehensible to all of us, and this time is the most difficult. Please hold Steve and me close to your hearts and in your prayers. I am shattered, shocked, enraged and so so sad.”

Meanwhile, the world of Tantra, which includes spiritual training in couples bonding and sex, was shaken to its core.

“They were so spiritual — she was not supposed to get sick,” said Sumati Caliway of Oakland, who attended the couple’s workshops in California and Costa Rica. “He was her rock. They are the last people that deserve something like that.”

Caliway said the Carters worked primarily with couples and were well liked and respected.

“Steve would lead guided meditations, and they’d be spiritual and deep, but funny, too,” Caliway said. “He had a lightness and playfulness about him. He was flirtatious in a really safe way. He made you feel attractive and loved without being sleazy. He was a really special person.”

Former Chronicle religion writer Don Lattin interviewed Lokita Carter and attended a Tantra workshop at Harbin Hot Springs in Lake County for a book he’s writing.

“The Carters and their network have suffered such a horrific string of tragedy since I interviewed Lokita,” Lattin said. In addition to Lokita Carter’s cancer diagnosis, he noted, Harbin Hot Springs was destroyed in the Valley Fire last month.

“And now this bizarre murder,” Lattin said. “My heart goes out to them.”