I have a theory, and speculation. I will quote IMSDB.com for the ROTS script... Notice Anakin's mood swing...... ANAKIN: NO!!! Just as MACE is about to slash PALPATINE, ANAKIN steps in and cuts off the Jedi's hand holding the lightsaber. As MACE stares at ANAKIN in shock, PALPATINE springs to life. The full force of Palpatine's powerful Bolts blasts MACE. He attempts to deflect them with his one good hand, but the force is too great. As blue rays engulf his body, he is flung out the window and falls twenty stories to his death. No more screams. No more moans. PALPATINE lowers his arm. PALPATINE: Power! Unlimited power! His face has changed into a horrible mask of evil. ANAKIN looks on in horror. PALPATINE cackles. ANAKIN: What have I done? ANAKIN sits. PALPATINE: You are fulfilling your destin, Anakin. Become my apprentice. Learn to use the dark side of the Force. ANAKIN: I will do whatever you ask. PALPATINE: Good. ANAKIN: Just help me save Padme's life. I can't live without her. I won't let her die. I want the power to stop death. PALPATINE: To cheat death is a power only one has achieved, but if we work together, I know we can discover the secret. ANAKIN kneels before PALPATINE. ANAKIN: I pledge myself to your teachings. To the w PALPATINE: Good. Good. The Force is strong with you. A powerful Sith you will become. Henceforth, you shall be known as Darth . . . Vader. ANAKIN: Thank you. my Master. PALPATINE: Rise, Darth Vader.