Curtis Broughton remembers the smiles and joy Australian tourist Lucas Fowler and American girlfriend Chynna Deese exuded during their chance meeting on a highway, and then the horror he felt when news reports described how the couple was shot dead hours later and their bodies left in a ditch.

Next Wednesday (July 15) marks the first anniversary of the senseless murders of Mr Fowler and Ms Deese.

The love-struck couple was on a road trip adventure across Canada when their blue 1986 Chevrolet van broke down on an isolated section of the Alaska Highway in northern British Columbia.

"They were happy, smiling, beautiful people," Mr Broughton, who was one of the last people to see Mr Fowler and Ms Deese alive, told AAP on Wednesday.

It was a warm afternoon on July 14 last year when Mr Broughton, his wife Sandra and sons Lewis, 11, and Mason, six, were driving home from a week-long camping trip in the Yukon.

The area was isolated, mobile phone coverage patchy and as the Broughtons headed south along the Alaska Highway near Liard River Hot Springs they spotted the broken down Chevy van.

Mr Broughton, a mechanic, pulled over to offer help.

Mr Fowler, the 23-year-old son of NSW Police chief inspector Stephen Fowler, was also handy under the bonnet and Mr Broughton was impressed.

The van's engine was flooded.

"He explained exactly what he thought was wrong and it made sense to me," Mr Broughton said.

"They had lots of food and lots of water and were just hanging out and having lunch."

The Broughtons continued home.

The next day Mr Fowler and Ms Deese, 24, from North Carolina, were found dead in the ditch near the van.

Police determined Kam McLeod, 18, and Bryer Schmegelsky, 19, who had quit their jobs at a Vancouver Island Walmart, were seeking notoriety and embarked on a murderous rampage.

They encountered the stranded Mr Fowler and Ms Deese and shot them multiple times with SKS semi-automatic rifles.

Four days later and 460km from where Mr Fowler and Ms Deese were murdered McLeod and Schmegelsky, seeking a new getaway car, came across 64-year-old University of British Columbia botany lecturer Leonard Dyck on the side of another highway.

They shot Mr Dyck dead, stole his Toyota RAV4, money and digital camera, set their own Dodge pick-up truck on fire and headed 3000km east to Gillam.

The teenagers recorded videos on Mr Dyck's camera.

In one clip recovered by police they described how they planned to hijack a boat and sail from Canada to Africa or Europe to elude authorities.

On July 23 the teenagers dumped the RAV4 on a gravel road outside Gillam, set it on fire and disappeared into the wilderness.

"Fear," Gillam local Clint Sawchuk, describing the feeling in the town when the car was found, told AAP.

"Two kids came to a town that 98 per cent of the time is very peaceful and all of a sudden all hell broke loose."

The Royal Canadian Mounted Police and Canadian military, including Royal Canadian Air Force CC-130H Hercules and a CP-140 Aurora patrol plane equipped with infrared cameras and imaging radar, flooded the area.

Mr Sawchuk slept with a shotgun to protect his family, and other residents also carried guns.

They avoided standing near windows in their homes for fear of being shot by the teenagers.

Mr Sawchuk, who runs sightseeing company Nelson River Adventures, made the breakthrough when he was taking a group of tourists along the river and spotted a blue sleeping bag tangled in willows.

RCMP officers joined him as they searched the area.

The teenagers ended their own lives in scrub near the river.

"After the bodies were found I just cut all communication with it," Mr Sawchuk said.

"I didn't watch the news.

"I was just glad it was over."

A truck driver who regularly drives along the Alaska Highway where Mr Fowler and Ms Deese were murdered placed a cross at the site last year.

It has inspired a memorial featuring Australian flags, cards, painted rocks, crosses and other items.

The young couple met backpacking in Croatia and their adventurous spirit touched the Broughton family.

"I did the same thing with my wife long before we even thought about getting married," Mr Broughton said.

"Two or three times we jumped in the truck and would be gone for two weeks or a month.

"We were about their age too.

"That's all they were doing.

"They were finding themselves."

Australian Associated Press