"He was a good guy, but he was so laboured by his sense of ethics and values and what's right. Being a good man is not good for you in the apocalypse. It's kind of a problem in this world," he said.
"I think one of the themes on the show is that the people are more dangerous than the zombies. The real danger in this world is how distorted humanity becomes when it's solely focused on survival.
"Morality, values and ethics all go out the window. It's about how you can survive the next 10 minutes and protect the people that are going to help protect you because you can't survive alone."
Fans quickly took to Twitter to voice their disapproval, with some suggesting he could yet return.
Curtis will begin filming four Avatar sequels later this year after being headhunted by director James Cameron.
He recently revealed he didn't have to audition for his role, wtih Cameron calling him out of the blue.
