SimonSays, on 13 March 2012 - 07:00 AM, said:
and another thing, I wonder if Carl witness Rick kill Shane, or did he just walked up and saw Shane on the ground. I think that would've made a huge difference to what he's thinking as he was pointing the gun to either Rick or Shane.
I think you're right about that. At any rate, let's consider Carl's perspective assuming he walked up after Rick killed Shane (since we don't hear Carl until he speaks the first time, we can only assume he wasn't standing there like a quiet idiot watching his dad kill his "other dad"). All Carl can see is Rick's back, hunched over another body. Remember that walkers tend to eat people while they lie on the ground. Carl may be under the impression that his dad is a walker eating a body, and even when he gets up, Rick is walking very slowly, like a walker. And when you're scared stiff, you may not consider things such as "he's talking, and walkers don't talk." But once he sees Shane up and moving, he realizes the contrast, AKA, Dad is alive, Shane is not. Again, nerves or fright might delay his gunshot, or maybe he's reluctant to kill Shane, even if he's dead already. Remember, Morgan couldn't shoot his own dead wife, and Herschel kept his dead wife in a barn for months.
That's my interpretation of the scene anyway.