"Even as we come to learn how this happened and who's responsible, we may never understand what leads anyone to terrorize their fellow human beings," Mr. Obama said.
"Such evil is senseless - beyond reason. But while we will never know fully what causes someone to take the life of another, we do know what makes that life worth living."
"[I]f there's anything to take away from this tragedy, it's a reminder that life is fragile. Our time here is limited and it is precious," he continued. "And what matters in the end are not the small and trivial things which often consume our lives."
In his remarks, Boehner said he was originally planning to talk about the economy but "life, they say, is what happens when you're busy making other plans."
"I know that when confronted with evil we cannot comprehend, Americans pull together and embrace our national family more tightly," he said.
"We join President Obama in sending condolences and prayers to the loved ones of those who were killed and wounded," Boehner added.
"And we all say 'thank God' for the police, the first responders, the doctors, and the nurses whose swift and heroic efforts saved lives."