Mr Hopkinson said it was too early to say whether the shooting was intentional or accidental.
Police were not aware of any imminent danger to public safety in the area, he said.
Homicide detectives have set up a large cordon and appear to be focusing their attention on a garage of one of three homes believed to be connected to the attack.
One neighbour told Toronto cable news station CP24 at the scene he heard screaming before the bodies were discovered.
"I didn't hear any words, but they were just screaming in pain or (because) he's sort of aggressive or something like that," Jerome Cruz said. "Then I heard another middle-aged man coming toward that screaming person and telling him to be calm, be quiet, things like that. Then I saw a lady coming out of the house running towards them."
Other neighbours told CP24 that they never imagined something like this could happen in their neighbourhood.