Police have arrested three people and recovered two firearms.
Four people were shot and wounded on Monday during a victory parade for newly-crowned basketball champions Toronto Raptors.
More than a million people were on the streets of the Canadian city to welcome the NBA (National Basketball Association) winners home, police said.
The shooting at about 15:45 local time prompted a stampede around City Hall Square where Prime Minister Justin Trudeau, Toronto Mayor John Tory and some Raptors players were on stage.
"We were kind of pushed up against a wall so we just had people squash us. We had nowhere to go. Even if you wanted to exit you couldn't. Just literally, stuck," a Raptors fan said.
Toronto Police Chief Mark Saunders later announced that three people had so far been arrested and that two firearms had been recovered.
Trudeau said on Twitter that he hoped for "a speedy recovery" for all those injured.
The mayor joined him in wishing for a quick recovery for the victims, adding that "those found responsible will be held to account to the full extent that the law permits".