NEW : `` These tragedies must end . At the same time , he expressed hope that the strength of community will make a difference . And to end them , we must change , '' Obama says . The president said the U.S. will work with other nations and international organizations "to help prevent these kinds of attacks from happening again." He vows action , saying America must do more to protect its children . NEW : The mother of a teacher being hailed as a hero calls her daughter `` selfless '' All victims at the Sandy Hook school were shot multiple times , a medical examiner says .
NEW : `` These tragedies must end . And to end them , we must change , '' Obama says . The president said the U.S. will work with other nations and international organizations "to help prevent these kinds of attacks from happening again." He vows action , saying America must do more to protect its children . NEW : The mother of a teacher being hailed as a hero calls her daughter `` selfless '' All victims at the Sandy Hook school were shot multiple times , a medical examiner says .