"And I looked, and behold
a pale horse: and his name
that sat on him was Death,
and Hell followed with him.
And power was given unto
them over the fourth part of
the earth, to kill with sword,
and with hunger, and with
death, and with the beasts
of the earth."
Revelation 6:8
This rider was named Death, plague
and pestilence will stalk the earth.
He is given power to destroy 1/4 of the people.
This starts the Great Tribulation.