One of the last people to see Australian tourist Lucas Fowler and his American girlfriend Chynna Deese alive says the couple was smiling, relaxed and sitting in arm chairs on the side of a Canadian highway.
"Obviously their van had broken down, but they were still happy and smiling," Curtis Broughton told AAP on Friday.
"They were having lunch or a bit of a meal when we pulled up."
Mr Fowler, 23, from Sydney, and Ms Deese, 24, from North Carolina, were found dead at the site hours later.
The Royal Canadian Mounted Police are treating their deaths as murder.
"It was terrible," Mr Broughton, recalling how he later discovered on social media the couple was found dead, said.
"We were shocked."
Mr Broughton, a mechanic, and his wife, Sandra, were driving home on Sunday about 3.20pm from a day visiting Liard Hot Springs, a remote area in northern British Columbia.
The Canadians saw Mr Fowler's blue 1986 Chevrolet van had broken down on the Alaska Highway, 20 kilometres south of the springs.
They stopped to offer help.
But after a quick chat with Mr Fowler he realised the young Australian had the problem under control.
"He seemed like he had everything diagnosed properly," Mr Broughton said.
"The vehicle was flooded out and they were going to try and get it going again until they could get the parts they needed."
The Broughtons got back in their car and drove home.
Mr Broughton said he did not notice anyone suspicious in the area when they stopped.
He called police as soon as he heard the horrifying news and realised he had spoken to the couple.
Ms Deese's brother, British Deese, told the Charlotte Observer their bodies were so badly beaten the family was told an open casket would not be allowed at his sister's funeral.
"This investigation is in its very infancy and it is not yet clear whether Lucas and Chynna were targeted or is this was a crime of opportunity," RCMP Sergeant Janelle Shoihet told reporters on Friday.
Mr Fowler's father Stephen is the NSW Police chief inspector for Sydney's north-west Hills district.
Two NSW detectives have flown to Canada to support the Fowler family, but they will not form part of the RCMP investigative team.
Mr Fowler and Ms Deese met at a hostel in Croatia two years ago and fell in love.
The globetrotters were on a road trip across Canada when tragedy struck.
The RCMP has asked for anyone who was on the freeway between 4pm Sunday, July 14, and 8am Monday, July 15, and could help with the investigation to come forward.
They are particularly interested in anyone with dashboard cameras.
Australian Associated Press