Swab the walls of that room for gunpowder residue…especially by the windows.
Yep. Someone shooting in the 2nd floor room would be shooting close to the left side of the window to avoid being seen by the SS Counter Sniper detail that likely were not in on the plot. Even after the FIB cleanup there may be gunpowder residue embedded in the paint or evidence of solvents used in this area in the cover up activity by assassination co-conspirators.
Who to trust to do the swabbing?