John van der Kiste: Emperor Francis Joseph - Life, death and the fall of the Habsburg Empire; Sutton Publishing 2005. It has an extensive list of sources, but they're not connected to specific chapters, so it's a bit of a mess.
And it was my mistake. It's actually in 1910, I misremembered (apologies for that) - between May 30 and June 5. Specifically, it is connected to the attempt on Governor Varesanin in June (the Emperor had been present on May 30 - the would-be assassin, one Bogdan Zerajic, claimed to have been present for the Emperor's visit - in fact, he had been followed by the local police, but managed to get close to the Emperor, later admitting he lacked the courage to go through with the act at the time).
So, less interesting of a moment than 1905, but still a good PoD.