Revelation 9:13-19 - A third of mankind was killed

9:13-15

Now the sixth angel blows his trumpet. In Rev 6:9 we read of the souls of the martyrs crying out from below the altar. There they asked how long it would be before God would avenge their blood. Part of what we are seeing here could be the avenging being carried out. The four angels who are at the Euphrates had been bound, but are now to be released. They are released to kill a third of mankind. Who these angels are is, as usual, something of a mystery, but it seems most likely that they are evil angels of some form or other.

9:16-19

We then see that a vast army has been released, and this was a terrible army. Fire, smoke and sulphur came from the horseman, signifying three plagues. And the three plagues killed a third of mankind.