A 41-year-old off-duty police officer was among the victims of the shooting, which happened about 5:19 p.m. Monday, the Toronto Star reported.
Soon after, an angry Police Chief Bill Blair told reporters two males, a youth and 20-year-old had been arrested several miles away at a subway station, and at least one weapon had been seized.
"It appears there was a dispute between individuals on the street," Blair said. "They took out guns and began shooting. It is infuriating that anyone would use firearms in a public place injuring innocent people."
Tuesday, Detective Sgt. Savas Kyriacou told a news conference that as many as 15 young people were involved in a wild shooting spree.
Police said one of the other victims was in critical condition, the Canadian Broadcasting Corp. reported.
There have been 78 killings in Toronto this year, including a record 52 involving firearms, the report said.