奥巴马：肇事者将被追究责任

US President Barack Obama has addressed the nation following the twin explosions at the Boston Marathon. The president said an investigation was still ongoing, and that the individuals or groups responsible would be held accountable. In a separate statement, a White House official said the twin explosions would be handled as an "act of terror."

"We still don’t know who did this and why they did this,” Barack Obama said. “We will hold them accountable.”