This question has been previously asked and answered. Please see the link below, and thank you for using eNotes.
The Bosnian Crisis of Serbia's ambitions and Austria-Hungary's intention to stop this ambition from disturbing her unity led to the annexing Bosnia and Herzegovinastria-Hungary by Au, thus ruining Serbia's dream of creating a pan-slavic kingdom. This leads to the assasination of Archduke Ferdinand and his wife Sophia, by a Bosnian terrorist that worked for the Black Hand Organization who was devoted to Serbia's cause.
The assassination of Archduke Frans Ferdinand and his wife.