One year ago: Pushing back against critics, President Barack Obama forcefully defended the temporary agreement to freeze Iran's disputed nuclear program, declaring that the United States "cannot close the door on diplomacy." Prosecutors closed their yearlong investigation into the shooting rampage at Sandy Hook Elementary School in Newtown, Connecticut, that claimed the lives of 26 victims; their report said the motive of gunman Adam Lanza, who also killed his mother and himself, might never be known.