Final answer:
Archduke Franz Ferdinand was assassinated by Gavrilo Princip, a member of The Black Hand, on June 28, 1914, in Sarajevo. This event was a significant trigger that contributed to the start of World War I.
Step-by-step explanation:
Archduke Franz Ferdinand was the heir to the Austro-Hungarian throne and was assassinated on June 28, 1914, in Sarajevo, the capital of Bosnia-Herzegovina. The assassination was orchestrated by The Black Hand, a secret Serbian nationalist group seeking the separation of Bosnia-Herzegovina from Austria-Hungary and its annexation by Serbia. Franz Ferdinand and his wife, Duchess Sophie, were killed by Gavrilo Princip, a 19-year-old Bosnian Serb nationalist who was a member of The Black Hand. This event set off a sequence of events leading to World War I, as Austria-Hungary's demands for restitution from Serbia after the assassination led to the activation of the complex alliance system in Europe.