Quebec provincial police say three women were killed early Thursday in separate incidents in Shawinigan.
Two women were killed in one residence and the third woman was killed in a nearby home in the city northeast of Montreal.
A man was wounded in the second incident but was able to flee the scene and alert a neighbour. He was then taken to hospital with life-threatening injuries.
A 51-year-old man was later arrested after he stopped the car he was driving at a gas station north of Shawinigan.
Provincial police say the suspect killer and the victims knew each other.
No names or ages have been released.