What did the assassin hope to accomplish?

Inevitably they got what they needed. After the Austrians lost the war the Austro-Hungarian Empire was disbanded. The Kingdom of Yugoslavia was built up on 1 December 1918 and the Conference of Ambassadors in Paris gave worldwide acknowledgment to the union on 13 July 1922.

They by one means or another trusted that by removing the leader of the Austrian snake, they would accomplish the 'freedom' of Serbia. All things considered, that was the hypothesis, at any rate - what they truly got was a gigantic intrusion by Austria, and World War I.