WATCH: President Obama's speech on the school massacre in Connecticut
"These tragedies must end"
On Sunday night, President Obama addressed an interfaith vigil for the victims of the mass shooting in Newtown, Conn., delivering a powerful call for the nation to take measures to prevent such tragedies in the future. "We can't tolerate this any more," he said. "These tragedies must end. And to end them, we must change." Watch the video: