The son of a senior NSW police officer and his American girlfriend have been found dead under suspicious circumstances in Canada.

The family of an Australian man and his American partner are searching for answers after the couple were found dead on the side of a Canadian highway in suspicious circumstances.

Lucas Fowler was found dead alongside his girlfriend, US woman Chynna Deese, on a remote stretch of the Alaska Highway, British Columbia, just as they were about to set off on a road trip around the “top half of the globe”.

Ms Deese had reportedly left her home to visit Mr Fowler, who had been working at a ranch in Canada, when tragedy struck.

Mr Fowler is the son of senior NSW police officer Inspector Stephen Fowler.

His family posted on Facebook their son had died in the “most terrible of circumstances” and they would travel to Canada to bring him home.

“We have lost our dear Lucas Fowler, son, brother, grandson and friend in the most terrible of circumstances. To lose someone so young and vibrant, who was travelling the world and just enjoying life to the full, is devastating,” the post said.

“To know his beautiful girlfriend, Chynna Deese of Charlotte, North Carolina also lost her life in this violent event is too cruel. All our love and best wishes go to Chynna’s family and friends.

“Our deepest thanks for all your love and care. At this stage we can only move forward a minute at a time, and those minutes are moving so slowly.”

Canadian police are appealing for any witnesses who might have driven past the couple’s blue 1986 Chevrolet van with Alberta licence plates that was sitting at the scene for days.

“Investigators are asking to speak with anyone who may have been travelling in the area of Liard Hot Springs, including any camping areas, and on the Alaska Highway 97 between Sunday July 14, at 4pm, to Monday July 15, 8am,” Sergeant Janelle Shoihet said in a statement this morning.

“We recognise this news is troubling for the entire community and absolutely appreciate there are concerns for safety, in an area that is popular with nature enthusiasts and tourists.

“This investigation is in its very infancy and it is not yet clear whether Lucas and Chynna were targeted or if this was a crime of opportunity.

“At this point, we have nothing to indicate that their deaths are linked to any other active and ongoing investigations in the area, or if there is a heightened risk to public safety.

“This is a unique circumstance and not one I am personally aware of in recent years.”

The stretch of road where Mr Fowler and Ms Deese were found on July 15 has been dubbed “Highway of Tears”. Between 18 and 50 women were murdered or went missing along the 724km of road since 1970.

The deaths have gripped British Columbia with fears a serial killer is responsible, initially sparking further concern the couple’s deaths could be linked to the murderer.

In 2015, signs along the highway warn of a serial killer on the loose, cautioning girls not to hitchhike, though the killer theory is only speculation.

Ms Deese’s sister, Kennedy Deese, wrote on Facebook the pair were “homicide victims along a remote stretch of highway in Canada while on a road trip”.

“No further information is available at this time, please do not ask. They were bright and beautiful souls. We are all still in shock and heartbroken.”

She followed up by saying, “it’s hard to understand the concept of a serial killer.”

Chynna’s brother wrote finding out his sister was dead was the most “chaotic day of my life” after she stopped responding to his text messages.

“My little sister left to visit her boyfriend Lucas for the ‘branding of the cows’ at a ranch he worked at in Canada and to travel through the top half of the globe,” he said on Facebook.

“24 hrs ago I found out why my little sis didn’t text me back. Chynna and Lucas’ lives were abruptly taken from a random act of violence while starting their road trip through Canada.”

Sgt Shoihet said investigators were “looking into any or all information” and for any witnesses or people with information to come forward.

“At this point the investigation is very early,” she said. “We’re absolutely committed to this investigation and it’s a priority for us.

“We’re trying to narrow down a timeline with respect to their deaths. Our investigators will consider any and all information carefully as the investigation progresses.”

NSW police confirmed the man “is the son of a serving senior officer and as such we are providing support to him and his family.”

“Öur thoughts are with them at this difficult time,” NSW Police said.

A woman from Fort Nelson, in British Columbia, claimed she had seen the couple with the van broken down on Sunday.

“This makes my heart so sad,” Sandra Broughton wrote on Facebook.

“We seen the blue van broke down on our journey home on Sunday and we stopped and asked if they needed help.

“I can’t believe that this young couple are dead now.”

Lucas Fowler studied at Ku-ring-gai High School while Ms Deese had gone to Appalachian State University and recently graduated with a degree in psychology and business.

Two NSW homicide detectives have been sent overseas to assist the investigation, liaise and support family members.

“The investigation into this incident is being led by the Canadian authorities and as such, they will be the appropriate source for information as it comes to hand,” the police statement said.

Canadian police are looking for anyone who saw the vehicle or offered assistance.

They’re also appealing for anyone that travelled the stretch of highway around the time of the discovery to come forward, according to a Royal Canadian Mountain Police media release.

The Department of Foreign Affairs and Trade confirmed they have informed the man’s family.

“The Department of Foreign Affairs and Trade is providing consular assistance, in accordance with the Consular Services Charter, to the family of an Australian man who died in Canada,” a spokesman said.

“Due to our privacy obligations we will not provide further comment.”