Why did the first attack fail to kill the archduke and his wife?

The assassination of Archduke Franz Ferdinand of Austria, heir presumptive to the Austro-Hungarian throne, and his wife Sophie, Duchess of Hohenberg, occurred on 28 June 1914 in Sarajevo when they were mortally wounded by Gavrilo Princip. Princip was one of a group of six assassins (five Serbs and one Bosniak) coordinated by Danilo Ilić, a Bosnian Serb and a member of the Black Hand secret society. The political objective of the assassination was to break off Austria-Hungary's South Slav provinces so they could be combined into a Yugoslavia. The assassins' motives were consistent with the movement that later became known as Young Bosnia. The assassination led directly to the First World War when Austria-Hungary subsequently issued an ultimatum to the Kingdom of Serbia, which was partially rejected. Austria-Hungary then declared war, triggering actions leading to war between most European states.