Well, the title, four horsemen is a slight giveaway.
The biohazard symbol on the nearest horse presuambly makes it Pestilance. The Pale horse is death, The Red horse is war, And the Black is death.
Revelation, chapter 6. The whole book is full of these visions of the apocolypse. The writer is though to have had a taste for hallucenogenic mushrooms, which could be quite funny, if it were not for the number of Americans who expect this to happen as written, in the next little while. Seemingly including the President, doing quite a bit to bring it about, but with mushroom clouds this time...
Honestly, do read Revelation. and be scared. The old translations sound right for it. They might not be as accurate to the oldest available texts as modern ones, but sound better.