What Was Mysterious Cloud That Turned Day Into Night in Eastern Russia?

— “At first it looked like it was a strong thunderstorm coming. The air went dark, and got darker and darker, but this time unlike anything else we have seen before the darkness had a rich yellow undertone.” - Local town official in Nizhne-Bytantaisky

— “Messages are going around about a light flash registered by the U. S. satellites, followed by increase of radioactive level and unusual activity of the military.” - Local resident in Eveno-Bytantaisky