The trigger cause of World War I was the assassination of Archduke Franz Ferdinand, who was next in line to be emperor of Austro-Hungary. He was killed in Sarajevo on June 28, 1914. He and his wife, Countess Sophie, both died. They were making a state visit to the capital of Bosnia. A Serbian secret society, the Black Hand, wanted Bosnia to break free from the Austro-Hungarian Empire and be a country by itself. They were supported by Russia. The Archduke and his wife arrived at 9:30 a.m. and got into an open-topped car at the train station. Members of the Black Hand had learned the route they would take to their destination. When the time came, one of them threw a hand grenade at the Archduke's car. It bounced off the back of the car, which drove on. It injured the driver and passengers in the car behind the Archduke instead. When the Archduke realized he was a target he immediately abandoned his planned trip and went to visit a hospital instead. However, the driver took a wrong turn up Franz Joseph Street and had to reverse. By chance, he slowed down in front of Gavrilo Princip, leader of the Black Hand. Seeing that this was his only chance to carry out his plan, he pulled his gun and fired, killing the Archduke, Sophie, who had been pregnant at the time. Gavrilo Princip was arrested and beaten up for this rebellious act. on the street in June 28, 1914. 