sarajevo is where the assassination of Archduke Franz Ferdinand happened, basically causing the 1st world war. 

a terrorist group, dedicated to serbian nationalism, planned the assassination of Franz Ferdinand. the man to carry out the assassination was on break and was going to get a sandwich when the driver of Franz Ferdinand's taxi(?????) took a wrong turn, ending up on the lane of the shooter, meaning Franz got shot.

Franz was already advised to stay away from Serbia as it was the national day of serbia, so tensions were already very high.