Russia says metro suicide bomb killed 14

Russian authorities Tuesday confirmed a suicide bomber was responsible for the metro blast that killed 14 people in Saint Petersburg, as the city began three days of mourning.Flags flew at half-mast in Russia's second city and flowers and candles piled up at an impromptu memorial outside the metro station rocked by the attack, as authorities beefed up security on the busy underground transport system.The Kremlin said the bombing was "a challenge to every Russian", including President Vladimir Pu