Spoilers ahead so be warned!
THR:Sophia (Madison Lintz) was in the barn the whole time! How come Hershel never mentioned it?
Robert Kirkman: I don't think that Hershel was ever doing a cataloging of the zombies. It was painful for him because his wife and son were also in the barn. It's not like he was actually hanging out in there or paying attention to all the walkers that were in there. He knew they were looking for a girl named Sophia but who knows what zombies were are in there and how often they'd been put in there. Otis (Pruitt Taylor Vince) was the one who was in charge and corralling them and putting them in there. So for all Hershel knew, Otis had put the Sophia zombie in there months ago.
THR: Was killing one of the comic's original characters an easy one?
Kirkman: When a good idea comes up, you have to go with it. Sophia is a character who is still alive in the comic book series and who has contributed quite a bit to the overall narrative and informed a lot of story lines for a lot of different characters. Having Carol (Melissa McBride) survive her daughter as opposed to the other way around as it is in the comics is going to lead to interesting but different stories.
THR: Will the second half pick up immediately after the shooting or will it jump ahead?
Kirkman: We're not going to be doing any big time jumps. Whether we lose a day, hour or if it picks up the very minute after the scene, I wouldn't want to give away too early but there's not going to be any massive time jump this season.
THR: How will Sophia's death alter Carl's development?
Kirkman: One of the major story lines in the comics is Carl's (Chandler Riggs) dissention into a darker role; he's forced into adulthood to make terrible decisions. His character evolving over the course of the comic book series is really going to be accelerated by the absence of Sophia. That will remain largely in tact and be sped up. There's going to be more darkness creeping in to the series in the second half of the season. Now that the Sophia question has been answered, they're not going to have that hanging over their heads and that's not going to be bogging them down making them have to devote time to that.
THR: Rick told Shane about Lori's (Sarah Wayne Callies) pregnancy, but not that he was aware of their affair. How long will he keep that over him?
Kirkman: I want the show to get a reputation as one that doesn't hang on to things like that for long. We have a lot of story to tell on this series and we're not going to be dwelling too much. I'm very excited that we got around to revealing that Rick knew about the relationship. Stuff like that is going to bubble up to the surface in very interesting ways in the last half of the season.
THR: Any update on when/if we'll see the Governor or Michonne?
Kirkman: I can say only that we will see them eventually. We will see some new characters popping up as early as the  premiere episode.
THR: Still unknown: What Jenner told Rick at the CDC. How much longer can you hold on to that?
Kirkman: It will be happening sooner rather than later.