Dion Lefebvre of Westlock, Alta., was driving his company's moving van on Highway 63 last Friday when a pickup truck passed him and smashed into an oncoming truck.
Lefebvre said he quickly pulled over to the side of the road and he and his co-worker, Eli Day, ran to the rescue.
The first thing they heard was a child crying. Lefebvre looked inside one of the trucks and found three-year-old Timothy Wheaton alive inside.
He unbuckled the boy and carried him to safety.
"Being a father, as soon as I heard Timmy crying, there was really no thought of not going in or not helping," said Lefebvre. "It was just doing what instinct tells me to do."
He said Day helped pull out the injured driver. Then Lefebvre pulled an 11-year-old girl from the other vehicle.
He said the driver of that truck was still alive. Along with other motorists who stopped to help, they attempted to open the crumpled door with crowbars and tried to put out the growing flames with fire extinguishers. But they couldn't reach him.
"Our efforts failed," he said. "We were just overwhelmed by flames."
Lefebvre grabbed moving pads from his van to use as blankets for the survivors as they sat and waited for help. He said it took almost an hour for emergency crews to reach the crash, which happened half way between Edmonton and Fort McMurray.
He later learned the 11-year-old girl died in hospital.
"We all hoped for the best," Lefebvre said. "My love and support goes out to the families involved."
The others killed include the parents of the three-year-old boy, his two-year-old brother, as well as a pregnant woman.
Since the crash, there have been renewed calls for the provincial government to finish twinning the busy stretch of road, which is the main link between Edmonton and the oilsands capital of Fort McMurray
There have been several deadly accidents on the highway. In 2006, the province announced that it would twin a 240-kilometre stretch, but only 33 kilometres have been constructed so far.
A protest rally is planned for Saturday in Fort McMurray.
Premier Alison Redford said earlier this week she will ask her new transportation minister, after cabinet is sworn in, to make twinning Highway 63 a priority.
"Shame on the government for not having it built already," said Lefebvre, who is often on the highway.
"If they were to put the same kind of intensity and integrity into building that highway as they did extracting the energy from the oilsands, it would have been built years ago."
— By Chris Purdy in Edmonton