Sushismom,
Indeed, two bombs were thrown at Alexander II that day, the second being the one that actually killed him. The first bomb was thrown at his carriage and wounded several in his escort. The Tsar got out to check on the wounded, despite pleas from his driver to flee. He also actually approached the bomber to ask if he had done it, and as he did another young man threw a bomb between himself and the Tsar, which mortally wounded both.