When Gavrilo Princip fired the lethal shots at Franz Ferdinand and Sophie in Sarajevo, who, because of their morganatic marriage, were not allowed in the shielded and covered Imperial Carriage (just like they couldn't sit together in the balcony at operas or orchestral performances, or attend many formal functions, etc.), but were in a convertible automobile (which Royals just didn't otherwise ride in at that time - in fact, prior to that, Teddy Roosevelt was the only sitting head-of-state, period, who had been known to tool around in an automobile), which made them easy targets - that's when, on re-evaluation from the original studies of him right after the war, and for quite a ways thereafter, the trauma and stress of his family tragedies caused him to act precipitously to King Petar I and Prime Minister Nicola Pavic of Serbia, just because it was AN ethnic Serb who pulled the trigger.