Marin County sheriff’s detectives are seeking three “persons of interest” in connection with the murder of a hiker off a trail near Fairfax.

Steve Carter, 67, was found shot to death Monday on the Old Railroad Grade trail, about 50 yards from westbound Sir Francis Drake Boulevard on White’s Hill, said sheriff’s Lt. Doug Pittman. The body was found by a hiker at about 6 p.m.

Carter was shot several times, apparently with a handgun, investigators determined. Bullet casings were found near the body.

Carter’s dog was with the body, the leash still in Carter’s hand. The dog was also shot but is expected to survive. The dog was turned over to the Marin Humane Society for care.

Investigators determined that the killer or killers stole Carter’s car, a silver 2003 Volkswagen Jetta station wagon with a California license plate of 6PPG662. The car, which had a dog carrier inside, remained missing Tuesday evening.

Investigators suspect Carter was killed not long before the hiker found his body. Authorities received a report of gunshot sounds in the area about 45 minutes earlier.

The sheriff’s department was trying to determine a motive for the slaying but said it could be a random attack. Investigators were able to find surveillance images of three people at a convenience store whom they are trying to identify for questioning. Investigators released two images showing a man and a woman; no clear images or description were available for the third person.

Anyone with information is asked to call the investigations unit at 415-473-7265 or the Crime Stoppers anonymous tip line at 800-222-TIPS. Crime Stoppers callers can be eligible for a cash reward for information leading to a conviction.

Carter, with his wife Lokita, was a former resident of Middletown in Lake County. Their business, the Ecstatic Living Institute, which specialized in tantric sex workshops, massage and vacations for couples, was based in Middletown.

Recently they had lived in Costa Rica before staying with friends in San Geronimo, according to a blog Lokita Carter maintained. The blog, “I am not my Body,” chronicled her treatments for breast cancer. She and her husband moved to Marin for treatment at Marin General Hospital’s cancer clinic.