The gunman walked down the busy avenue firing.
Thirteen others ranging in age from 10 to 59 were wounded.
"We do not know why this happened", Toronto Police Chief Mark Saunders told reporters on Monday.
Toronto councillor Paula Fletcher said of the incident: "It's not gang-elated".
There was a shooting on a street in Toronto in Canada on Sunday night.
As of now, it is not known how the gunman was killed.
Authorities did not release information about the shooter, or offer any possible motive.
Toronto Police statistics show that, to July 14, there had been a total of 220 shootings with 27 fatalities so far this year, against 196 with 17 deaths for all of 2017. A victim has also died from injuries sustained in the attack.
"And then, I saw the carnage as I ran down the street here to kind of follow the gunfire", the man told the station, who described the scene as "pretty insane".
The unit, which investigates police-involved shootings, said officers located the man on a cross street "and an exchange of gunfire took place".
The suspected shooter is dead, according to police. He also says a young girl is in critical condition. "It's way too early to rule out anything".
Toronto Mayor John Tory called the shooting an "unspeakable" act and said the time had come to confront the rising prevalence of guns in the city, which has experienced a spike in shootings in recent weeks.
Multiple people have been rushed to hospital after the Toronto shooting when a gunman opened fire in the city's Greektown neighbourhood.
There is a heavy police presence at the scene and a large swath of the area has been blocked off as emergency crews respond to the situation. But local television station CP24 is showing images of multiple ambulances and other first responders at the scene, with several people being treated by paramedics.