Patrick Shunn and Monique Patenaude worried about getting on the wrong side of the man who lived a little ways up an old logging road from their 21-acre spread along the Stillaguamish River.

When they sued other neighbors over a property dispute more than two years ago, they avoided naming him as a defendant because they didn't want to irk him, their former lawyer said Monday.

But now the couple is missing and presumed murdered, and investigators are trying to track down the man, John Blaine Reed, 53, along with his brother, Tony Clyde Reed, 49. Snohomish County Sheriff Ty Trenary said surveillance video linked them to the dumping of the victims' cars over an embankment in a remote, wooded area near Oso, about 50 miles north-northeast of Seattle.

Both brothers had previously been convicted of felonies, the sheriff's office said, though it did not release details about their backgrounds.

"They weren't looking forward to any kind of conflict with Mr. Reed," the couple's former lawyer, Thomas Adams, said Monday. "They didn't want to provoke any kind of an issue with him."

Neighbors reported Shunn, 45, and Patenaude, 46, missing last Tuesday, after noticing that their animals had not been cared for. A crew in a Snohomish County Sheriff's Office helicopter found their vehicles two days later a few miles north of their home in the foothills of the Cascade Mountains.

After searching the vehicles and the home where John Reed recently lived, detectives concluded the couple had been murdered. Their bodies have not been found, but investigators continued searching Monday.

They were also looking for the Reeds, whom they described as armed and dangerous. John Reed's car was found in Ellensburg, in central Washington, on Saturday, and detectives said the brothers had taken their parents' red 2007 Volkswagen EOS Coupe, with Washington plates AXH5106.

The grim mystery played out on land abutting the nation's worst landslide disaster, the 2014 Oso landslide, which wiped out a rural neighborhood and killed 43 people. In an interview shortly afterward, John Reed told The Seattle Times he watched the slide as it roared past his front yard.

"This mountain of dirt taller than any trees near me cut off my view like a curtain," he said. "And it shot right in front of me, right by my house."

The county bought out Reed's house last month to ease any risks from future flooding, but investigators believe Reed had been returning to the home since then, the sheriff's office said.

Sheriff's spokeswoman Shari Ireton said she did not have information about any controversy between Shunn and Patenaude and John Reed, but that others had described it as a property dispute.

In 2013, Shunn and Patenaude joined two other property owners in suing neighbors David and Shelly Dick over the use of the old logging road, which crosses their property. They alleged that the Dicks had been allowing people to trespass on their land with recreational vehicles so that they could access an unoccupied riverfront parcel owned by the Dicks.

Last month, the Dicks filed a motion asking the court to dismiss the complaint.

John Reed's property was further along the logging road, and he too used it regularly, but the couple didn't want to sue him, Adams said. It's possible he had a right to use the road because of his historical practice of doing so, Adams said, but the couple was also concerned because of things they had heard about him — though exactly what they had heard remains unclear.

John Reed has been cited for a number of mostly minor offenses, including driving without a license and collecting wood without a permit, for which he was fined $87. He served five years on Department of Corrections supervision in the late 1990s for attempting to elude police in Whatcom County.

Tony Reed has amassed dozens of arrests and twice was under state supervision — from 1989 to 1991 on drug charges, and from 1994 to 2003 for three misdemeanors, one count of attempting to elude police and one count of third-degree assault.