Prime Minister Stephen Harper is reacting with sadness to the "awful" shooting rampage at Sandy Hook Elementary School in Newtown, Conn.
A U.S. official says 27 people are dead, including 18 children.
Harper reacted on Twitter, just minutes after finding out about the massacre.
He wrote, "The news is just awful. The thoughts and prayers of Canadians are with the students and families in Connecticut affected by this senseless violence."
Foreign Affairs Minister John Baird did the same, saying: "Deeply sad over the sickening news out of Newtown. Our thoughts are with our American friends during this most difficult time."
Public Safety Minister Vic Toews wrote "Our hearts go out to the victims of the Newtown shooting and their families. Today is a time for mourning and not politics."
Parents flooded to the school about 100 km northeast of New York City, looking for their children in the wake of the shooting.
Students were told to close their eyes by police as they were led from the building.