Rick definitely shot the fat dude in the head even after he was down from the first shots. I don't remember if he did that to the other guy though.
That was gross when the guy got his face bitten off. The walker just chomped down on his nose and ripped it off. Ewwww. I liked how the flesh was peeling off the walker's face as he tried to get Lori though the windshield. Nice attention to detail.