Moscow (CNN)Monday's deadly St. Petersburg metro attack was carried out by a suicide bomber originally from the central Asian Republic of Kyrgyzstan, authorities said.
- Russian Prime Minister Dmitry Medvedev described the blast as a "terrorist act."
- Train driver praised for actions that likely saved lives.
- President Vladimir Putin was in St. Petersburg earlier on the day of the attack.
- Flowers and tributes laid at memorials Tuesday as three-day period of mourning began.
- Some metro stations reopened after a complete network shutdown.