Police are investigating the shooting in Oshawa, east Toronto which saw five people dead, including the suspect.
Neighbours reported hearing the sound of gunshots at around 1.20am on Friday, said a police spokesman.
The dead include four males and one female, two of whom were under the age of 18.
Toronto Police said a 50-year-old woman was also rushed to hospital with a gunshot wound where she was treated for a non-life threatening injury.
“All deceased members were known to each other,” said the police in a statement.
“Investigators believe the suspect died from a self-inflicted gunshot wound and no other suspects are outstanding.”
Constable George Tudos told the BBC police found a “chaotic scene” inside the home.
“We’re not saying too much because we’re still at the early stages of the investigation,” he said.
Carol Gibson who lives near the family, told CBC they were “very caring”.
She said: “They were a family that cared for each other quite a bit.
“If they weren’t playing baseball, hockey or shooting hoops on the driveway, they were out raking leaves and they did it as a family. A very caring family.”
Homicide Unit investigators are working with the Coroner’s Office to confirm the identities of everyone involved.