The bus drivers' union identified the killed driver as 49-year-old Sylvain Ferland. He died after the vehicle he was driving collided with a BMW sedan and another car around 6 p.m. ET about two blocks from the Montreal airport.
Ferland was thrown from the bus, which tipped over in the crash, pinning him underneath. It took four hours for his body to be extracted from the wreckage. A 61-year-old woman who was in the BMW's passenger seat also died.
Union spokesperson Tom Mouhteros said many of the Montreal transit corporation's 3,300 drivers are in shock.
"In 23 years, 24 years here, I haven't seen something like this, where a bus driver dies in an accident like this. It's just something that's beyond belief right now," he said Wednesday.
Mouhteros, with Local 1983 of the Canadian Union of Public Employees, said investigators don't yet know what caused the collision, or how the bus flipped over.
"It is rare. It can happen, buses could flip over just like any other vehicle. Eighteen-wheelers flip over," he said. "That's for the police to find out exactly what happened."
An official with Montreal's ambulance service said he's never seen such an accident in his three decades on the job.
"After 30 years, you see just about everything. But... this kind of impact where the bus is on its side like that, no, I haven't seen that," Urgences Santé operations chief Robert Lamle said.
Ferland was driving a bus on Route 196, which runs from the Côte Vertu metro station south to Lachine. The crash happened at 55th Avenue and Lindsay Avenue, an industrial area in the community of Dorval in the western part of Montreal.
Cars and trucks often drive quickly along 55th Avenue, a four-lane road that runs through low-lying warehouses and businesses.