GOLDEN, B.C. - A horrific crash on the Trans-Canada Highway in British Columbia over the long weekend ripped through two families from Edmonton who were on their way to the Vancouver area, leaving an 11-year-old boy without his parents and siblings.

Six people were killed late Sunday morning when the minivan they were travelling in slammed head-on into an RV on a straight stretch of highway east of Golden, B.C., a small mountain community located about 250 kilometres west of Calgary.

The victims' names haven't been officially released, but the RCMP said they were members of two families from Edmonton who were travelling together in two separate vehicles on their way to Abbotsford in B.C.'s Lower Mainland.

However, relatives have identified victims as 47-year-old Arshad Mahmood, his wife Shakila, their 13-year-old daughter Malika and another 15-year-old daughter. The family had moved to Edmonton from Pakistan in 2006.

A 14-year-old girl from the second family, identified as Elizeh Shah, along with her grandfather, were also killed.

Sami Monir, a friend of both families, said the boy had switched vehicles so Shah could ride along with his older sisters.

Monir said he was in Abbotsford with a friend waiting for the two families to arrive when a truck driver phoned them with news of the crash. They immediately drove to Golden, where they met the young boy and the father of the other family.

"He's 11 years old. He was holding spirits pretty high," Monir said in an interview.

"He was very confident. He came out and met us and basically thanked us for visiting him. He was actually giving us the courage because we were all really devastated."

Monir said the boy is staying with the Shah family until relatives arrive from Pakistan and Dubai.

"We have an 11-year-old child who has now lost his entire family," RCMP Cpl. Dan Moskaluk said in an interview. "The highest priority now is dealing with and assisting with the families involved."

Investigators had ruled out speed, alcohol and road conditions. The van will also be inspected this week for any signs of mechanical failure.

But accounts from witnesses, who said the van appeared to drift into the lane of oncoming traffic without any attempt avoid the RV, led police to focus on driver fatigue or inattention as possible factors, said Moskaluk.

"It didn't move slowly, it tended to slowly drift over -- that's indicative of a person who has fallen asleep or a person who is inattentive," he said. "When a person is conscious, there is usually a reaction and a correction, that being an application of brakes or a steering correction. In this case, witnesses said the vehicle had simply drifted over."

Two people in the RV were treated for non-life-threatening injuries.

Moskaluk said four of the six people in the van weren't wearing seatbelts, but the crash proved too severe even for the two who were buckled in.

A photograph of the scene released by the RCMP showed the twisted wreckage of the minivan in the middle of the highway. The RV was sitting several metres away, with a large section below the windshield ripped off and scattered along the pavement.

Golden Mayor Christina Benty said she was in church Sunday morning when she heard the blare of sirens rush past, heading east out of town on a busy section of highway that has seen more than its share of deadly collisions over the years.

"We just heard siren after siren after siren, and we know this was bad," recalled Benty.

"We hear the sirens going out of town on a regular basis, and every time we do, there is a collective lurching in the stomach. ... Being a community on the No. 1 Highway, we hear the sirens too often."

The winding Trans-Canada Highway around Golden has a reputation as an especially treacherous section of roadway, listed by the Canadian Automobile Association as one of the 12 most dangerous spots in the country.

However, police said the crash happened along straight section of highway with fresh pavement, so neither road conditions nor the design of the highway were considered factors in this case.

Based on the RCMP's description of where the accident occurred and the photograph of the scene, Benty said it appeared the crash wasn't on the most dangerous part of the highway just outside of town.

"It (the apparent crash site) is not that initial maybe 10 kilometres outside of Golden that's just twisty and turny through the Kicking Horse Canyon there," she said.

"It is a well-travelled highway, a lot of Albertans travelling into B.C. for holidays."

The federal and B.C. governments are currently funding a $970-million highway upgrade between Golden and the Alberta boundary.

With a report from CTV British Columbia's Mike Killeen