For much of the 20th century, Western historiography and Balkan historians would hold radically different views of the Sarajevo assassination and the role of Young Bosnia and the Serbian government in it. Let’s look for a minute at what really happened before going into its many interesting interpretations.
Gavrilo Princip, a 19-year-old Bosnian Serb, is undoubtedly the lynchpin of the plot as well as the one who actually carried out the assassination. A high school student studying “abroad” in Belgrade, Serbia, Princip dreamed of heroic service to his nation. This goal must have seemed difficult to attain. A frail young man, he had been rejected for service in the Serbian army during the Balkan wars, and he must have suspected that he would not live a very long life. (He died of tuberculosis in 1917.) Participating in an assassination plot against an Austro-Hungarian official must have seemed like the perfect act of national service and personal self-sacrifice that he was seeking. Check out a wonderful, recent CNN article for "7 Things You Didn't Know about Gavrilo Princip." http://www.cnn.com/2014/06/27/opinion/7-things-gavrilo-princip-man-who-started-wwi/index.html
In spring 1914, he made contact with an organization that would support such a project, a Serbian society known as ‘Unification or Death’ or ‘the Black Hand.’ This shadowy group, working independently of the Serbian government but supporting its claims to Serbian-inhabited territories outside of the country, was headed by a controversial figure: Colonel Dragutin Dimitrijević, code named ‘Apis.’ The head of Serbian military intelligence, Apis worked without his government’s approval to sponsor an assassination in Bosnia. The Black Hand helped plan the assassination, provided weapons to the conspirators, and assisted the students in smuggling the weapons across the Austro-Hungarian border.
The Serbian government’s discovery of the plot put them in an awkward position. On the one hand, Serbia couldn’t just come out and admit to the Austrians the embarrassing fact of the complicity of one of the Serbian government’s own officials. On the other hand, Serbia stood a lot to lose if the plot was successful (since Austria was probably looking for a pretext to declare war against its smaller neighbor). The compromise solution – providing vague warnings to Austria of a possible plot without admitting to knowing any specifics about it – would later make Serbia look guilty of masterminding an attack on the Habsburg monarchy.
Princip was joined in the plot by two fellow 19-year-old Bosnian students in Serbia: Nedeljko Čabrinović and Trifko Grabež. After crossing into Bosnia, they were joined by others. Danilo Ilić, 25 years old and a sometime school teacher, helped recruit two Sarajevo high school students: Vaso Čubrilović and Cvjetko Popović, who were 16 or 17 years old at the time. (Sources vary on their exact age.) A young Bosnian Muslim man in his mid-20s, Muhamed Mehmedbašić, also joined the group. On the day of the assassination, all except Ilić brought weapons to the parade; Ilić was also on hand to supervise.
The day of the Archduke's visit was June 28, Vidovdan, the anniversary of the Serbian defeat by the Ottoman Empire at the Battle of Kosovo in 1389. It was an inauspicious day for a royal visit by another conquering power. Franz Ferdinand had been warned about a possible attempt to his life, but it was a beautiful, sunny Saturday morning, his wife was next to him, and everything seemed peaceful and serene.
An excellent description of what happened next - and a map of the event - are found at a Brigham Young University webpage. Read from “The Visit.” http://net.lib.byu.edu/~rdh7/wwi/comment/sarajevo.html