Well from the RotS script:
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.
Well true Zoltan, but they also had Maul as dead too as per TPM script and look how that turned out.
OBI-WAN jumps up out of the pit, calls QUI-GON's lightsaber to him, throwing
DARTH MAUL off. The young JEDI swings with a vengeance, cutting the SITH
down. DARTH MAUL falls into the melting pit to his death.
Originally posted by Zenwolf
I guess, still though think I'd rather have something else to confirm it too.
What are you looking for exactly?
There's also this:
After Jackson adjusts his performance, completing another convincing death scene, the crew applauds.
—The making of Star Wars Episode III Revenge of the Sith