Cooper produced and published Behold a Pale Horse in 1991. The book has been influential among "UFO and militia circles". According to sociologist Paul Gilroy, Cooper claimed "an elaborate conspiracy theory that encompasses the Kennedy assassination, the doings of the secret world government, the coming ice age, and a variety of other covert activities associated with the Illuminati's declaration of war upon the people of America". In Behold a Pale Horse Cooper proposed that AIDS was the result of a conspiracy to decrease the populations of blacks, Hispanics, and homosexuals.