Motorists called city police and the Royal Canadian Mounted Police about 1 p.m. Monday, reporting that a tractor-trailer was weaving into oncoming westbound traffic on the Yellowhead Trail highway, the Edmonton Sun reported.

Witness Zack Novak, 45, told the newspaper he followed the truck for about 10 miles.

"He had many opportunities to cross the median and come back to the eastbound lane but he didn't," Novak said.

Witness William Acevedo said he saw the driver as he swerved to avoid being hit.

"He looked angry. He looked mad. He looked zoned out," Acevedo said.

Numerous cars swerved off the road to avoid the truck before it hit a concrete overpass barrier, skidded along it and fell 30 feet onto train tracks, the report said. The truck landed upside down and burst into a fireball, witnesses told police.

The driver was pronounced dead at the scene and wasn't immediately identified, the report said.