On June 28, 1914, Bosnian Serb revolutionary Gavrilo Princip assassinated the heir to Austria-Hungary's throne in Sarajevo. The death of Archduke Franz Ferdinand set in motion events that led to the start of World War I one month later. Princip was convicted of treason and murder but could not be sentenced to death because he was believed to be under the minimum age of 20. He was given a 20-year sentence and imprisoned in a fortress near Prague, but his life did not outlast the end of the war. A historian describes the assassin's torturous years there.