'Walking Dead' renewed, Glen Mazzara out as showrunner Just in time for the end of the world, AMC has quite a surprise for fans of "The Walking Dead." The megahit series has been renewed for a fourth season but will continue without show runner Glen Mazzara, making the show's top creative post about as safe a place as the world after a zombie apocalypse. In a statement Friday announcing the show's return - all but a foregone conclusion, given its record-setting ratings - AMC also dropped the bombshell that Mazzara would no longer be involved with the series beyond the current season, which returns to the network in February. "The two parties have mutually decided to part ways," AMC and Mazzara said in the joint statement. Glen guided the series creatively for Seasons 2 and 3. The statement points to creative disagreements between Mazzara and the network: "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 as show runner and executive producer. Given the show's gangbuster ratings - its mid-season finale drew a whopping 15.2 million viewers, making it the first cable series to win the fall season in the much-coveted 18-to-49 demographic - a shakeup of this magnitude was unexpected. Mazzara is the second show runner in just three seasons to part from "The Walking Dead" under mysterious circumstances. Series creator Frank Darabont left the show during the production of Season 2. When Darabont exited, rumors swirled about budget conflicts and the show's creative direction. Some fans and critics grumbled about a perceived meandering pace in the second season. Rather than bring in a marquee name to steer the ship, AMC promoted staff writer Mazzara who plenty of experience as an executive producer, including on NBC's quirky cop show "Life" and TNT's hospital drama "Hawthorne." Under his direction, the show appeared to be back on track narratively and soared in the ratings. AMC has quickly established itself as the premier destination for serial drama on television with shows like "Mad Men" and "Breaking Bad." But it also has developed a less welcome reputation for alienating its behind-the-scenes talent. Shortly before Darabont's ouster from "The Walking Dead," for instance, the network was locked in a tense and highly public contract dispute with "Mad Men" auteur Matthew Weiner. Shawn Ryan, creator of the acclaimed FX series "The Shield," tweeted Friday morning: "With FX, Showtime, HBO, Starz, Cinemax, A&E, TNT and others to sell to, it's a real question now why good show runners should sell to AMC?" A possible point of contention between Mazzara and the network could be over the level of violence in the program, which is already among the most blood-soaked dramas on television. "The Walking Dead" is adapted from a popular series of comic books by Robert Kirkman, who is also an executive producer on the series. The show has at points deviated significantly from the source material, perhaps most notably by keeping Judith, the infant daughter of protagonist Rick Grimes, alive. Every single one of my writers has asked us to kill off that baby. I'm dragging my feet," Mazzara told The Times in an interview in November. That baby's survival right now is a necessary win because otherwise it is too bleak.... Whatever the case may be, AMC and the show's creative team are maintaining a public show of unity - for now, anyway. "My time as show runner on 'The Walking Dead' has been an amazing experience, but after I finish Season 3, it's time to move on," Mazzara said in a statement. Mazzara was not available to elaborate about the reasons for his impending departure, but his personal publicist Karlyn Nelson reiterated that "looking forward to Season 4 there were creative differences." For his part, Kirkman said: "I am in full support of both AMC and Glen Mazzara in the decision they have come to and believe the parties came to this decision in the best interest of the future of the show. ... I believe the future is bright for 'The Walking Dead.'"