"Serbia Nationalists comminted the perfect murder"
A murder yes, but not so perfect...
http://www.historyhouse.com/in_history/ferdinand/
Nedelko Cabrinovic, managed to get his nerve up and lob a bomb at the Archduke's car. Sadly, he had no aim and hit a neighboring car, injuring several in the crowd quite badly but not harming the Archduke at all. Nedelko quickly swallowed a cyanide capsule and jumped in a nearby canal. Had Nedelko done a few calculations beforehand, it would have saved a great deal of embarrassment. The poison had long since expired and the river was only ankle deep. An angry crowd pulled the vomiting Cabrinovic from his chosen gutter. Hearing the bomb, the last three conspirators all assumed that their target had been killed and wandered off to a local pub to get drunk in celebration.
Furious, Franz Ferdinand confronted the mayor of Sarajevo at City Hall saying, "Mr. Mayor, one comes here for a visit and is received by bombs! It is outrageous!" The mayor looked around frantically and burst into his prepared speech: "Your Royal and Imperial Highness!...Our hearts are full of happiness..." Smile and nod, Mr. Mayor, smile and nod. Later in the afternoon, the Archduke decided to go visit the victims of the morning's bomb in the hospital. His confused driver, however, took a wrong turn and drove right past Schiller's -- the pub in which the other conspirators were busy drinking away.
Gavrilo Princip, a young revolutionary once turned down by the Serbian Army for being too "small and weak" raised his pistol, shot twice and killed the Archduke and his wife.
Had Gavrilo not stayed and dawdled at the pub talking to a friend, the Archduke could very well have completed his stay in Sarajevo without further event