Answer:
Prior to the outbreak of WWI, a Serbian secret nationalist resistance group assassinated the Austria-Hungarian heir to the throne.
Step-by-step explanation:
The man who shot the achduke Franz Ferdinand of Austria and his wife in Sarajevo was a Bosnian Serb man named Gavrilo Princip. He was a member of a secret society that called for autonomous southern Slav rule and liberation from the Austrian empire.