Chynna Deese, 24, and her Australian boyfriend, 23-year-old Lucas Fowler, were found dead last week on the side of Alaska Highway 97 in a remote part of Canada. They had reportedly been fired at, the back window of their blue Chevy blown out by a shotgun blast.
Stetson Deese, Chynna's brother, said the couple loved going on adventurous trips around the world.
"It's like a nightmare that we'll never wake up from," Stetson told "CBS This Morning." "They were both extremely nice, both very optimistic and also spontaneous."
Fowler's father, a New South Wales police chief inspector, immediately flew to Canada with his family after learning about his son's death.
"It's just devastating and our heart goes out to the whole of [Chynna's] family," said Stephen Fowler. "We're just crushed."
The couple's bodies were found about 20 miles south of a hot spring popular with tourists. Alandra Hull, a highway maintenance worker, said she saw the couple shortly before they were believed to have been killed, having a heated argument with a bearded man.
"If you just get a bad feeling, and that’s what I had, you just don’t stop,” Hull told 9News.
Hull said she was working with a police sketch artist in an attempt to produce an image of the man.
By Monday evening, police had released a sketch of a man investigators want to speak with in relation to the couple's deaths. The sketch showed a bearded man with a cap on his head. Investigators believe he was driving an old Jeep Cherokee with a racing stripe on the roof and are asking the public for help identifying him.
Chynna and Lucas were also spotted by two passersby picnicking by the side of the road. He was trying to fix a mechanical problem with the van, Curtis and Sandra Broughton said.
“There was a van broken down on the side of the road, and we pulled over to see if they needed help,” Curtis told Global News.
"They seemed like they kind of had it under control,” added Curtis.
Police are also investigating a possible link between the couple's deaths and the disappearance of two teens, and the discovery of an unidentified body, in the same region.