The Snohomish County Sheriff's Office in Washington State says it is searching for two men they believe killed former B.C. woman Monique Patenaude and her husband Patrick Shunn.

Patenaude, 46, and Shunn, 45, were last seen on April 11.

"Detectives are asking for the public's help in locating 53-year-old John Blaine Reed and his brother, 49-year-old Tony Clyde Reed," said a release on Sunday. "Both men are convicted felons and are believed to be armed and dangerous. Their current location is unknown."

The office says detectives found video surveillance connecting the Reed brothers to the disposal of Shunn and Patenaude's vehicles.

The Snohomish County Sheriff's Office said both vehicles appeared to have gone over an embankment not far from each other in a remote, wooded area.

'Homicidal violence'

"Detectives believe the couple were the victims of homicidal violence based on evidence collected at the scene of the missing couple's vehicles, as well as the former residence of John Reed," said the release.

Search and rescue teams continue to search for Shunn and Patenaude in a large area north of the homes of the victims near Oso.

"The recovery of Patrick and Monique is our agency's number one priority right now, for the sake of their families," said Sheriff Ty Trenary. "Our second priority is getting the Reed brothers into custody and off the streets."

Friends in B.C. say Patenaude met Shunn at the Burning Man Festival in Nevada, and for many years they each commuted between Canada and the U.S. before Patenaude moved to Washington State about three years ago.

Concerned neighbours called police after Monique Patenaude, 46, and her husband Patrick Shunn, 45, went missing from their home in Washington state. (Shari Ireton)

Cynthia Fawcett says she and Patenaude worked together as care aids for people with developmental disabilities for more than two decades in Burnaby, B.C.

"All of us family and friends are totally devastated with the news," she said. "I want to find these two guys and I want some answers and I want to find my two friends."

Police say a vehicle belonging to John Reed in Ellensburg was recovered on Saturday and they also confirm that the brothers are in possession of a red 2007 Volkswagen EOS Coupe with Washington plates AXH5106, which belongs to their parents.

John Reed is five-feet, eight-inches tall, 190 lbs. with hazel eyes and grey hair. Tony Reed is five-feet, 11-inches tall and 150 lbs., with green eyes and grey hair.

Anyone with information about John or Tony Reed, or the disappearance of Shunn and Patenaude, is asked to call the Snohomish County Sheriff's Office anonymous tip-line at 425-388-3845.

Snohomish County police say they're trying to recover bodies of couple, no longer a missing persons' case <a href="https://twitter.com/cbcnewsbc">@cbcnewsbc</a> <a href="https://t.co/lN1JiyOFsv">pic.twitter.com/lN1JiyOFsv</a> —@KamilKaramali

With files from Kamil Karamali