It has been prophesied thousands of years ago, and IMO we are living in the end times today. I don’t think we have to worry about billions being killed. It is going to happen and the clues as to how it will happen seem very clear, at least to me.
Revelation 9:13-16New International Version (NIV)
13 The sixth angel sounded his trumpet, and I heard a voice coming from the four horns of the golden altar that is before God. 14 It said to the sixth angel who had the trumpet, “Release the four angels who are bound at the great river Euphrates.” 15 And the four angels who had been kept ready for this very hour and day and month and year were released to kill a third of mankind. 16 The number of the mounted troops was twice ten thousand times ten thousand. I heard their number.
Silverngold