"Germans from Russia" are ethnic Germans, not Jewish.
The Latvia theory, suggested by some in this thread, is the likely scenario.
Königsberg should not be considered here, as it was never part of the Russian empire. They held it for only a couple of years in mid-1700's, before turning it back to Prussia. It became part of the Soviet Union only after WWII with all ethnic Germans deported and people from Soviet the Union were moved there to repopulate the city (possibly only ethnic Russians).