Authorities are investigating a third body discovered on the same stretch of highway in Canada where an American woman and her Australian boyfriend were found murdered, 7 News reports.

On Monday, the bodies of 24-year-old Chynna Deese and her 23-year-old boyfriend, Lucas Fowler, were found along the Alaska Highway in British Columbia.

A third body was discovered Saturday at a rest stop near the Stikine River Bridge.

Deese and Fowler, who were on a road trip through Canada, were found shot to death. Deese is from Charlotte, North Carolina, while Fowler is from New South Wales, Australia.

Police reportedly believe they were killed between July 14-15.

On Saturday, officers from the Royal Canadian Mounted Police were attending to a truck fire when a driver passing by alerted them to the third body, according to the report.

Police are investigating whether all three killings are related.

Witnesses told the news station that  Deese and Fowler appeared cheerful and relaxed on Sunday, even through their blue van had broken down. Curtis Broughton told 7 News he and his wife were driving home after visiting Liard Hot Springs when they saw the van pulled over. They offered to help, but Fowler said he could manage.

“He seemed like he had everything diagnosed properly,” Broughton said, adding that the pair looked relaxed and were sitting in chairs next to the highway.

“They were still happy and smiling,” he said. “They were having lunch or a bit of a meal when we pulled up.”

Broughton said he was shocked upon learning the couple’s fate the following day.

“It was terrible,” he said.

In a statement, the Fowler family said Lucas’ death has been “devastating.”

“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.

“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.”

Authorities are asking for the public’s help. Anyone with information about the case is urged to the Northern Rockies Royal Canadian Mounted Police at 250-774-2700 or Crime Stoppers at 1-800-222-8477. Investigators are especially interested in any video of the area where the bodies were found.

[Feature image: Chynna Deese and Lucas Fowler/NSW Police Force]