Final answer:
Gavrilo Princip, a member of The Black Hand, assassinated Archduke Franz Ferdinand and his wife on June 28, 1914, leading to the outbreak of World War I due to a series of political alliances and disputes between the major European powers.
Step-by-step explanation:
Archduke Franz Ferdinand was assassinated by Gavrilo Princip, a member of the Serbian nationalist group The Black Hand. This act was carried out on June 28, 1914, during an official visit by the archduke and his wife to Sarajevo, with the ambition to separate Bosnia-Herzegovina from Austria-Hungary and annex it to Serbia to create a larger Serbian state. Princip, who was only nineteen at the time, saw an opportunity when the archduke's motorcade took a wrong turn and ended up stuck in traffic outside of the café where Princip was present. Seizing the moment, he fatally shot both the Archduke and his wife Sophie.
The assassination set off a chain of events that led to the outbreak of World War I. Austria-Hungary's demands for restitution from the Serbian government were rebuffed, leading to the former's invasion of Serbia, which then triggered the European alliance system. This intricate network of alliances led to the involvement of major powers like Germany, Russia, France, and eventually Great Britain, catalyzing the conflict into a full-scale global war.