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

The father of an Australian man who was found dead alongside his American girlfriend in northern B.C. last week issued an emotional plea for information on Monday.

A road worker discovered the bodies of Lucas Fowler and Chynna Deese on remote section of the Alaska Highway some 20 kilometres south of Liard Hot Springs last Monday.

"He came to Canada and he planned a trip in a van with Chynna," Fowler's father, Stephen Fowler, told reporters in B.C. on Monday.

"It's a love story that's ended tragically. It's the worst ever love story. We have two young people who had everything ahead of them who have been murdered."

Fowler called his son "a fun-loving guy," adding that his experience as a police officer in Australia couldn't have prepared him for the trauma of Lucas's death.

"I may be an experienced police officer, but today I'm standing here as the father of a murder victim," Fowler said.

"Nothing prepares my family for what we are going through now."

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

On Monday, the RCMP confirmed that both Fowler and Deese had been shot and killed.

Over the weekend, a witness told Australian media she'd seen the couple in a heated exchange with a bearded man a short time before their deaths.

Mounties have 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.

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.

Stephen Fowler echoed the call for information Monday.

"However little—please contact the police," he said.

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