Any fan of AMC's 'The Walking Dead' likely knows of the show-runner struggles the series has had over the years, first with the sudden and shocking exit of executive producer Frank Darabont, and most recently the announcement that AMC would bring back the mega-hit zombie series for a fourth season without Darabont's replacement Glen Mazzara at the helm. Yet unlike last time, has the reason for Mazzara's departure come to light? Find out why Glen Mazzara left 'The Walking Dead' inside!

While we wait for 'The Walking Dead' to resume its third season with February 10 episode "The Suicide King," fans are still in shock that show-runner Glen Mazzara will depart the series in advance of the show's fourth season. Yet while Frank Darabont's departure remains something of a mystery, new details have come to light regarding the reason for Mazzara's exit, largely pointing to 'The Walking Dead' comic creator and AMC executive producer Robert Kirkman:

Several insiders confirm that Kirkman, whose detailed graphic novels form the basis of the series, is "very proprietary," as one puts it. One adds, "I believe Robert wants to maintain a certain amount of his control, and AMC needs Robert for the fan base." But despite the vitriol, some sources involved with Walking Dead say Kirkman was one of several producers on the show who had issues with Mazzara and his vision.

One source says Mazzara's shortcomings in running the series during the most recent third season became "abundantly clear … especially for the second half of the season." This source says production was shut down "several times" because of a lack of material.

Few would argue that Mazzara's vision led to the widely-embraced improvement in the show's third season, so it isn't entirely clear what could have changed in the second half of 'The Walking Dead's third year. Kirkman himself was at the center of recent controversy with 'Sons of Anarchy' creator Kurt Sutter, who has several times attacked AMC and Kirkman's handling of the situation in defense of former colleague Mazzara.

Well, what say you? Do you believe that Glen Mazzara's exit from 'The Walking Dead' has more to do with Robert Kirkman, or shortcomings in the back half of the season? Who do you think should handle the show as it moves into season 4? Give us your thoughts in the comments!

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