A man walked along a Toronto street firing a handgun into restaurants and cafes, shooting 14 people and killing two before dying after an exchange of gunfire with police.

Police Chief Mark Saunders did not rule out terrorism as a motive, though officials did not immediately identify the attacker, other than to say he was 29 years old.

Toronto police spokesman Meaghan Gray said early Monday that a second victim had died, though there were no further details.

Saunders earlier said that a young woman had died in Sunday's shootings and that a girl aged 8 or 9 was in critical condition. The condition of the other victims was not known yet.

"This is an attack against innocent families and our entire city," Toronto Mayor John Tory said in a city council meeting Monday.

The mass shooting in a usually peaceful city comes three months after a driver of a van plowed into pedestrians on a Toronto sidewalk, killing 10 people and injuring 14 and amid increasing concern about gun violence.

A video from one witness shows a man dressed in black clothes and a black hat walking quickly and firing three shots from the sidewalk into at least one shop or restaurant in Toronto's Greektown, a lively residential area with crowded Greek restaurants and cafes.

Witnesses heard many shots and described the suspect walking past restaurants and cafes and patios on both sides of the street and firing into them.

Prime Minister Justin Trudeau tweeted that his thoughts were with everyone affected.

"The people of Toronto are strong, resilient and brave - and we'll be there to support you through this difficult time," Trudeau tweeted

Our prayers go out for the victims of this tragic event.