June 28th 1914 Sarajevo, Bosnia and Herzegovina. Archduke and heir to the throne of the Austro-Hungarian Empire Franz Ferdinand and his wife were driving through Sarajevo in a motorcade. Then a serb named Gavrilo Princip shot Ferdinand and his wife before getting immediately arrested.
Following the assassination Austro-Hungary declared war on Serbia. Their actions would lead to the start of the so called "Great War", what would be later known as World War I, a conflict which would claim somewhere between 9 and 17 million lives.
Below: Painting depicting the assassination.