The police officer father of Lucas Fowler says his family is "crushed" by the deaths of the 23-year-old and his American girlfriend, Chynna Deese, whose bodies were found on the side of the Alaska Highway in British Columbia.

Key points: Chief Inspector Stephen Fowler spoke about his loss while in transit to repatriate his son Lucas' body from Canada

Chief Inspector Stephen Fowler spoke about his loss while in transit to repatriate his son Lucas' body from Canada NSW Police confirmed Lucas and his girlfriend Chynna Deese were shot dead

NSW Police confirmed Lucas and his girlfriend Chynna Deese were shot dead Ms Deese's family has called for police to step up efforts to find the killer

The Royal Canadian Mounted Police (RCMP) have confirmed the deaths were a double homicide.

In transit at Los Angeles airport on his way to Canada to repatriate the body of his son, Chief Inspector Stephen Fowler said he and his family were devastated.

Stephen Fowler said his family were appreciative of the support they had received. ( Supplied: Channel 9 )

"He's a loss to so many people and his girlfriend, it's just devastating and our heart goes out to the whole of her family, we're just crushed," he told Nine News.

"It's been fantastic, the support we've had from family and friends ... we're just in a very bad place."

Canadian police want to speak with anyone who may have travelled in the area of Liard Hot Springs and on the Alaska Highway 97 between the afternoon of Sunday, July 14, and the following morning, especially anyone with dashcam footage.

NSW Police Assistant Commissioner Mark Jones said on Saturday they had been told the young couple was shot in "what can only be described as horrific circumstances".

Chynna Deese's family has called for more to be done to track down their daughter's killer. ( Supplied )

'This was someone's son, someone's daughter'

Meanwhile, Ms Deese's family has called for swifter action to track down their daughter's killer.

"I want this to be personal, this was someone's son, someone's daughter," her mother Sheila told the American Broadcasting Company.

"She always came home at some point and it just doesn't seem real because in my mind, I'm hoping she's going to come home."

Ms Deese's brother British added: "This is not enough, there's a huge safety concern with people travelling in Canada and around that area ... it's very concerning."

"I don't know who would do something like this ... we're never going to get full closure on this and it's going to hurt the rest of our lives."

A blue minivan with Alberta registration plates was found at the scene of the murders. ( Supplied )

Canadian Broadcasting Corporation (CBC) reporter Roshini Nair said the incident had shocked the local community.

"This stretch of the highway ... is a very popular tourist destination and a homicide like this is very unprecedented," she said.

"Northern British Columbians are super friendly and super excited to see all these people who come from all over the world and so to see this ... incident happen, it's very shocking and upsetting.

"We spoke to the ranching couple that had hosted Lucas Fowler as a ranch hand and they were devastated, they thought he was such a lovely person and he had just left on Saturday from their home."