Ottawa: A police officer was killed when a shooter opened fire west of Toronto on Monday, an official said.
One other person also died, according to local media, and at least three people were wounded in the violence.
"I'm horrified by today's senseless violence, including the killing of a Toronto police officer," Ontario Premier Doug Ford said on Twitter.
Just before 4:30 pm (2030 GMT), police issued an alert about an armed suspect who fled a strip mall in Mississauga, Ontario in a stolen vehicle after a shooting.
Moments later, police in nearby Milton said they had arrested the suspect following another shooting in that town.
Police in Mississauga told AFP two people had been shot, but would not confirm that one of them had died.
Milton police meanwhile tweeted that "1 person has been pronounced deceased at the scene and 2 others have been transported to hospital."
Canada has been rocked by several incidents of mass violence in recent years, including a stabbing spree in a remote Saskatchewan Indigenous community on September 4 that left 10 dead and 18 wounded.
One of the suspects in that case was found dead, believed to have been murdered by his brother, who was later arrested after a four-day manhunt and died in custody.
A gunman masquerading as a policeman also killed 22 people in Nova Scotia in April 2020 - including a police officer - two years after a driver of a van killed 11 pedestrians in Toronto.
And another shooter killed six worshippers at a Quebec City mosque in January 2017.
