Will Smith performs 'Summertime' on Colbert
Amber Alert issued for Montana teen
TPP May Fail if Renegotiated, Singapore Warns US
Boko Haram's new leader is son of executed founder, insider says
Obama declares Trump 'unfit' for presidency
Teaser Trailer for Christopher Nolan's 'Dunkirk' Debuts
Katy Perry Releases Empowering Olympic Anthem,