Police were called about an "active male shooter who had shot several victims" at a condominium in Vaughan, less than 50 km (31 miles) north of downtown Toronto, at about 7:20 p.m. local time on Sunday (0020 GMT on Monday).
Police found and fired at the suspect in a hallway and he was pronounced dead about 40 minutes later, a spokesperson for Ontario's Special Investigations Unit (SIU) told reporters on Monday.
Authorities then recovered dead bodies from several floors as well as a semi-automatic handgun that is suspected to be the weapon used in the shooting, authorities said.
Vaughan Police Chief Jim MacSween said the suspect had been identified as Francesco Villi, a resident of the building. No information was shared about any potential motive.
The York Regional Police Department said it was working to confirm the identities of the victims and inform their families. Vaughan is located in Ontario's York region and has a population of about 320,000.
The SIU, which investigates deaths involving police, said it was looking into the suspect's death and that a post-mortem was scheduled for Tuesday.
Canada has much stricter gun laws than the United States, but Canadians are allowed to own firearms providing they have a license. Restricted or prohibited firearms, like handguns, must also be registered.
Reuters