McGuinty has issued a statement describing the shooting as a "senseless and cowardly act of violence that resulted in a tragic loss of life."
Quebec's premier-in-waiting, Parti Quebecois leader Pauline Marois, was whisked offstage during her victory speech in Montreal after two people were shot outside the hall where she spoke. Police later announced one had died.
McGuinty says the thoughts and prayers of Ontarians are with the families of the victims and the people of Quebec during this difficult time.
Marois led the PQ to a minority government, ousting the Liberals but making it difficult for the party to pursue its independence agenda.
McGuinty says the people of Ontario and Quebec are friends as well as neighbours and the two provinces will continue to work together as they have in the past.
In the statement, he said all Quebec party leaders ran a "robust campaign" and also paid tribute to outgoing premier Jean Charest, who lost his seat in the election.
"He has been a strong partner for Ontario and a good friend to me," McGuinty said of his fellow Liberal leader. "His years of public service in Ottawa and Quebec have made our country even stronger."
"All of us in Canada are privileged to live in a country with free and fair elections — something many around the world continue to struggle to achieve," McGuinty said.
After the shooting Tuesday night, police arrested a 62-year-old suspect wearing a mask and a housecoat who shouted in French, "The English are waking up!"