Well, Gavrillo and his co-conspiritors planned to kill Archduke Ferdinand with a thrown bomb, which the Archduke defected with his arm. The bomb exploded without doing much harm, and only later by pure chance the Archduke drove by Gavillo and was shot. It's a miracle that the assasination worked at all, the story is full of incompetence from the assassins. As such the parallel to the Great Cannon fits perfectly.