AMC says it has renewed its Georgia-set zombie drama "The Walking Dead" for a fourth season but executive producer Glen Mazzara won't be returning.

"The two parties have mutually decided to part ways," AMC and Mazzara said Friday in a statement to Variety. "Glen guided the series creatively for Seasons 2 and 3. AMC is grateful for his hard work. We are both proud of our shared success.

"Both parties acknowledge that there is a difference of opinion about where the show should go moving forward and conclude that it is best to part ways. This decision is amicable and Glen will remain on for post-production on Season 3B [the second half of the third season] as show-runner and executive producer."

"I am appreciative and grateful to Glen for his hard work on 'The Walking Dead.' I am supportive of AMC and Glen's decision and know that the series is in great hands with one of the most talented and dedicated casts and crews in the business. I look forward to the show's continued success," executive producer Gale Anne Hurd said in her own statement.

The show stars Andrew Lincoln, Norman Reedus and David Morrissey as leaders of survivors of a zombie apocalypse.