Global News quoted a Toronto police source as saying the suspect is believed to have opened fire at police before being shot and killed.
Ontario's Special Investigations Unit is also on scene investigating. "One young girl in critical condition", Toronto police said on Twitter, adding that all 14 victims were shot with a handgun.
Thirteen others have also been rushed to a local hospital for treatment.
Toronto police tweeted that the shooting occurred in the Danforth and Logan avenues area of Greektown, a busy residential area with restaurants and cafes. "We just ran", said John Tulloch, who was on Danforth Avenue for a nighttime walk with his brother at the time, to The Gobe and Mail.
"The people of Toronto are strong, resilient and courageous - and we'll be there to support you through this hard time", he continued.
Another witness told the CBC News that she was at Christina's restaurant with her family when they heard shots and were asked to run into the restaurant.
"I'm not calling it random", said Toronto Police Chief Mark Saunders.
Toronto Police Chief Mark Saunders earlier said a woman died in the attack and a young girl was critically injured.
Fletcher said: 'It's not gang related. "We still live in a great city", he said, "but we have to be ever more vigilant about this kind of things". "It looks like someone who is very disturbed".
Toronto Mayor John Tory arrived on the scene and thanked first responders for their efforts.
The Toronto Police have confirmed that one person is dead as a result of this shooting, not including the alleged shooter himself.
The Sunday incident follows another tragedy in Toronto in April, when a driver of a van plowed onto a sidewalk, killing 10 people and injuring 14.
Police are asking anyone who may have witnessed the shootings or may have video or information about the shooting, they are asked to contact police. Authorities haven't released his name or disclosed his possible motivation.