Novelization
The novelization of the film by Michael Avallone retained the original scripted ending. Brent does not kill General Ursus. Taylor confronts him and Dr. Zaius. As Taylor tries to reason with Zaius, Zaius condemns him and Ursus repeatedly shoots Taylor with his pistol; Brent's rifle empties and the gorillas kill him. Ursus is horrified, telling Zaius that he has emptied the pistol into Taylor; he should be dead, but he still lives. Knowing he is dying, Taylor (after Zaius refuses to help him) decides to stop the violence by detonating the bomb. This he does, destroying the Earth itself.
Read more about this topic: Beneath The Planet Of The Apes