Police say 18-year-old Rueshad Grant was standing beside a parade float Saturday night when he was run over by the vehicle just before 9 p.m.
It was earlier reported that Grant had been riding on the float when he fell under the vehicle`s wheels.
Officials are examining a video posted on the Internet showing the immediate aftermath of the incident, with spectators yelling for the float to stop as it slowly starts moving after a brief pause.
Grant was rushed to hospital, but died soon after.
Parade organizers have expressed their "heartfelt sympathies" to those who knew the young man.
"We are deeply saddened by this loss," spokeswoman Denise Herrera-Jackson said in a statement.
"The Toronto police are conducting a full and thorough investigation and we will assist them in any way we can."
An autopsy had been scheduled for Sunday.
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