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 said the shooting in the city's Greektown neighbourhood was not random and he did not rule out terrorism as a motive.
"Other than the shooter, we have a young lady that is deceased," the police chief said.
A video from one witness shows a man dressed in black clothes and hat walking quickly and firing three shots from the footpath into at least one shop or restaurant. Toronto's Greektown is a lively residential area with crowded Greek restaurants and cafes.
The condition of the other victims was not known, police spokesman Mark Pugash said.
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.
John Tulloch said he and his brother had just left their car when he heard about 20 to 30 gunshots.
"We just ran. We saw people starting to run so we just ran," he said.
An army of police, paramedics and other first responders soon descended on the scene, while area residents, some in pyjamas, emerged from their homes to see what was happening.
Toronto Councillor Paula Fletcher said she heard that the gunman was emotionally disturbed.
"It's not gang-related. It looks like someone who is very disturbed," Fletcher said.
Councillor Mary Fragedakis also said she heard the gunman was disturbed.
Mass shootings are rare in Canada's largest city.
"We were so use to living in a city where these things didn't happen," Toronto Mayor John Tory said. "But there are things that happen nowadays and they are just unspeakable."
This past weekend Toronto police deployed dozens of additional officers to deal with a recent spike in gun violence in the city. Tory said the city had a gun problem.
"Guns are too readily available to too many people."
Police urged people to provide video or witness testimony.
The mass shooting came a few months after a van driver ploughed into pedestrians on a Toronto street, killing 10. Authorities have not disclosed a motive.