I've heard DeMunn decided to leave the show with Frank Darabount. But later he changed his mind and decided he wanted to stay in the show. Unfortunately it was too late because the scripts had already been written.

 

Oh, well that's just...sad. I heard that Darabont's departure was sudden and unexpected (didn't the AMC execs let him know he was being given the boot while he was on the road promoting the show (or very shortly after)?), so I could see why Jeff DeMunn might want to leave as well. After all, Darabont brought him into the show, along with Laurie Holden and Melissa McBride. I remember when Laurie Holden acted out her final scene, I was wondering if she would still be with TWD if Darabont had still been involved.

I guess it's all part of the industry. Still sucks, though.