A couple say they stopped to help Australian man Lucas Fowler and his American girlfriend Chynna Deese before they were murdered on a Canadian highway.
Dashcam video could hold the key to finding the killer who shot dead the son of a senior NSW police officer on the side of a Canadian freeway.
Lucas Fowler and his American girlfriend, Chynna Noelle Deese, were found dead on Monday on the Alaska Highway, 20 kilometres south of Liard Hot Springs, British Columbia.
The Royal Canadian Mounted Police are calling it a double homicide.
An old blue van Mr Fowler and Ms Deese were driving appears to have broken down on the highway and at least one Good Samaritan couple stopped to help in the hours before they were murdered.
"This makes my heart so sad," local 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."
Mr Fowler is the son of the NSW chief inspector for Hills district in Sydney's northwest, Stephen Fowler.
The family issued a statement on Friday night confirming Lucas' death "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," they said.
"We are all now travelling to Canada to be with our boy and to bring him home."
NSW Police sent two homicide detectives to Canada to assist the investigation, liaise and support family members.
The RCMP released photos of Mr Fowler and Ms Deese on Friday and issued a request for witnesses and video from motorists who may have had dashcams.
"Police would like to speak to anyone that may have travelled this stretch of highway between Sunday, July 14, 2019 at 4.00pm and Monday, July 15, 2019 at 8.00am," the RCMP said in a release.
"Police would especially like to speak with anyone who may have a dashcam video while travelling that area.
"A vehicle, an older blue minivan with Alberta plates, was found at the scene and police would like to speak with anyone who may have seen the vehicle or rendered assistance."
Dashcam video from motorists will give authorities insight into vehicles and other clues on the highway at that time.
The Broughtons said they contacted the RCMP.
"Usually when someone is broke down along the Alaska Highway, Curtis (being the helpful mechanic ) usually stops and asks if everyone is ok and if they need help," Ms Broughton wrote.
"Yes he contacted the RCMP and let them know that we see and talked to them after we left the hot springs."