Sketch Released In Hunt For Answers To Murdered Aussie And Girlfriend

The father of an Australian man, shot dead after his Chevrolet van broke down on the side of a remote highway in Canada has made a plea for help to solve the murder.

Lucas Fowler, 23, and his American girlfriend Chynna Deese, 24, were gunned down on the side of the Alaska Highway in British Colombia a week ago.

The blue 1986 Chevrolet van the pair had been travelling in had broken down after they stopped to let it rest.

Canadian couple Curtis and Sandra Broughton came across the "happy and smiling pair" on Sunday afternoon, offering them food and water before heading on their way.

The following day, Fowler and Deese were found dead on the roadside, killed in what police said: "can only be described as horrific circumstances".

On Tuesday morning, Canadian Police released a sketch of a man they want to speak to over the deaths.

After confirming the couple had been killed with a gun, Royal Canadian Mounted Police Sergeant Janelle Shoihet said the bearded-man in the composite was spotted speaking to the couple before they were killed.

She told reporters that she did not know about a reported heated exchange.

"My understanding is there was a conversation that's why investigators to speak with this person," she said.

Fowler's father Stephen, a senior NSW police officer, also pleaded for public help to solve the crime that he said has "torn two families apart".

“It is the worst ever love story," he said. "Because we now have two young people who had everything ahead of them tragically murdered.”

READ MORE: Mystery Mounts Over Murdered Australian Lucas Fowler And Girlfriend

"We are hopeful of a positive outcome and obviously we are appealing, along with the RMCP, for anyone to contact who may have any information whatsoever," he continued.

"However little, please contact the police."

NSW police chief inspector Stephen Fowler
as he fronted the media on Tuesday, pleading for public information. Photo: AAP

Some reports have speculated they could have been victims of a serial killer, after the discovery of another body -- 470km away from where Fowler and Deese were found dead -- near a burning red and grey Dodge pick-up truck, and the disappearance of two teenagers.

While police have repeatedly stressed they have no evidence the cases are connected, authorities have urged the public to stay vigilant.

With AAP.