Once every year, the Deer catch human beings.
They do various things which irresistibly draw men near them; each one selects a certain man.
The Deer shoots the man, who is then compelled to skin it and carry its meat home and eat it.
Then the deer is inside the man. He waits and hides in there, but the man doesn't know it.
When enough Deer have occupied enough men, they will strike all at once.
The men who don't have Deer in them will also be taken by surprise, and everything will change some.
This is called "takeover from inside".