WARNING: SPOILERS AHEAD! Do NOT continue reading if you have not watched episode 3 of “The Walking Dead.”

Episode 3 of “The Walking Dead” ended with a major bombshell on Sunday – Karen and David’s killer was revealed. But fans of the AMC series can't be certain that the person who came forward really killed the pair.

So, who was the killer? None other than a longtime group member, Carol.

When asked by Rick if she was the one that killed Karen and David, Carol responded with a simple, “yes.” But the theory that fans have is that Carol may have been covering up for someone else – the young girl, Lizzie.

Viewers are speculating that Carol may have burned the bodies but didn’t kill them. Instead the thought is that Lizzie killed the victims and Carol burned the bodies to cover it up.

While it’s an interesting theory, there are definitely a few flaws in it. Lizzie doesn’t seem like a normal young girl (who can really be considered normal during a zombie apocalypse?), but she’s also a suspect for the person that has been feeding rats to the prison fence walkers. Although the identity of that person hasn’t been revealed yet, it seems strange that Lizzie would kill two humans but cry about walkers getting killed.

Furthermore, in interviews executive producer Robert Kirkman made it seem as if the mystery of Karen and David’s killer was a closed case. Kirkman told the Hollywood Reporter that the “horrific act” is something that Carol’s “thought long and hard about and has decided that it’s something that definitely needs to be done.”

“She’s very prepared and capable of whatever can come from this, and she’s ready for it,” Kirkman said of the repercussions of “playing God” in the prison. “This is something that really illustrates the evolution of this character and how much of a different person she is now.”

Fans can definitely agree that the character of Carol has evolved from the quiet domestic violence victim from season 1. During this season alone, Carol has defied the council and been secretly teaching the children of the camp how to use weapons and protect themselves. In episode 2 she almost allowed young Lizzie to put a knife in her father’s head so that way he wouldn’t wake as a walker. Carol no longer relies on anyone else to get a job done, proving that to Rick in episode 3 when she ignored him and tried to fix the water hose in a zombie-ridden field.

Is Carol’s evolution for the better? Or will she become a liability for the prison … developing some Governor-esque qualities?

Do you think Carol really killed Karen and David? What are your thoughts on Lizzie? Tell us your theories in the comments section.

New episodes of “The Walking Dead” air on AMC on Sundays at 9 p.m. ET.