Your wrote, "He left the world through a window high up in his private house."
Sorry, Susan, you appear to be misinformed. My information is that Berthier was staying in the Bamberg royal palace which is known as the New Residence, so it is easy for mistakes to be made. This is a large building with lots of rooms. It was at the time of Berthier's death the residence of Berthier's father Duke Wilhelm.
As I recall, the meeting between the Russians officers and Berthier occurred at the Residence with Duke Wilhelm being the host. So, the Russians would have been aware of exactly where Berthier was located. I think that this signal event occurred just the day before Berthier's death.