July 23 update: Kam McLeod and Bryer Schmegelsky are now considered suspects in three deaths in northern B.C., Mounties say.

Mounties say a man and woman found dead in northern B.C. last week had both been shot.

According to police, Australian Lucas Fowler and his American girlfriend, Chynna Deese, were on a road trip in a blue, 1986 Chevy van when a road worker discovered their bodies on remote section of the Alaska Highway some 20 kilometres south of Liard Hot Springs last Monday.

The victims were publicly identified on Friday. Their deaths were initially considered suspicious, but Mounties have since said they're treating the case as a double-homicide.

Over the weekend, a witness told Australian media she'd seen Deese and Fowler—who were 24 and 23 years old—with a bearded man a short time before their deaths on Highway 97.

Alandra Hull said she'd driven past them Sunday evening, and saw what appeared to be a heated exchange.

Hull said the couple appeared to be bothered by the man.

"To me he kind of looked frustrated or something," she told Nine News Australia.

In an update of Monday, Mounties released a sketch of the man seen with the couple.

The RCMP said investigators want to speak to the man, but emphasized that he is not considered a suspect in Fowler and Deese's deaths.

He is described as a white man with darker skin and dark hair with a possible beard or glasses.

Police said the man is shorter than Fowler, who stood 6'3" and may be associated with an older model grey Jeep Cherokee with a black stripe on the hood and a black light/bull bar with small, covered lights. He is believed to have been travelling south.

Mounties have also released security footage of the couple at a Fort Nelson gas station taken on the Saturday before their deaths.

The video, shot from two different angles, shows the couple arriving in the van at 7:30 p.m. Deese can be seen washing the windows while Fowler fills up. The couple is then seen driving away from the gas station at 7:47 p.m.

B.C. Premier John Horgan addressed the case Monday, offering his condolences to the families of the victims.

"Certainly, to the two individuals who were travelling in Peace Country and were found murdered, our hearts go out to the families," he said.

Fowler, the son of an Australian police officer, had been working on a ranch near Hudson's Hope. The owner told CTV News Fowler and Deese had been planning a road trip to Alaska in the blue van police found at the scene.

The investigation is ongoing, and the RCMP is looking to speak to anyone who'd seen the couple or the van. Anyone with dash cam video is also asked to come forward.

Tips can be left with the Northern Rockies RCMP at 250-774-2700 or anonymously through Crime Stoppers.

With files from CTV News Vancouver's Kendra Mangione and David Molko

We’re now hearing from Lucas Fowler’s father, Stephen Fowler: a police inspector in Australia who today acknowledges he stands here as the father of a murder victim. No tip is too small he said. “It’s a love story that’s ended tragically... it’s the worst ever Iove story.” pic.twitter.com/s4nmCSjBBR — David Molko (@molkoreports) July 22, 2019

This man is not a suspect police say. But they want to speak w him. They believe he’s driving older model Jeep Cherokee with a black racing stripe and a bar with small lights. Was traveling SB. @BCRCMPMedia will also release Fort. Nelson gas station video of couple from Jul 13 pic.twitter.com/gNdXAMtjTU — David Molko (@molkoreports) July 22, 2019