Halloween genocide

When we arrived, we found the land already occupied.
So, we introduced diseases into the population, and waited.
People died, crops died.
And after five years, the land was ours.
We put on environment suits and explored the countryside.
Abandoned villages full of rotting bodies, nature reclaiming the paths and clearings.
Crews cleaned up one location after another, establishing colonies.
Until there was no sign of the previous population. Only us.
We had conquered the world.
That’s when a light appeared in the sky.
Two. Five. Dozens. Thousands.
They scattered glowing capsules everywhere.
And we clutched our throats and screamed.