A man shot dead another man at a day care centre in Quebec then killed himself.
The 53 children present were evacuated unharmed, but police said some may have watched the killings.
For a moment, Canada feared its own version of last year's deadly school shooting in the US, where 20 young children were killed.
Police received a call about an armed man with a shotgun threatening people, Gatineau Police Chief Mario Harel said. They arrived to find one man dead with a shotgun beside him and a second man, an unidentified employee of the day care, also dead.
He said the shooting seemed to be related to a recent separation between a couple but did not give further details.
The day care centre is located in two homes, and Sergeant Jean-Paul LeMay said police found a body in each one. He said the children were safe at a nearby house.
Police were investigating the link between the men and the possibility of domestic violence, he said. He would not say if either was linked to a child at the day care.
Police speculated that some children likely witnessed the killings.
Parents sobbed and hugged while they waited for police to bring them to their children. Omar Eltalawi rushed to the scene from his nearby home as soon as he heard about the shooting, fearful for his three year-old daughter, Zain.
"It was horrible," he said as he described the fear of not knowing what was going on inside the centre. You see these things on the news and you don't expect it to happen to you."