Whose assassination started World War I?

Franz Ferdinand and his wife Sophie were visiting Sarajevo, the capital of Bosnia, which Austria-Hungary had annexed in 1908. Earlier that morning, a member of a group of young Bosnian Serb conspirators threw a bomb that bounced off their car. Later, the driver took a wrong turn and stopped right in front of 19-year-old Gavrilo Princip, who fired two shots, killing both the archduke and Sophie. Austria-Hungary blamed Serbia and declared war on 28 July 1914. Within about a week, alliances had pulled in Russia, Germany, France and Britain, turning a regional crisis into a world war.