I don't get some of that. The guy killed the other "gang member", but didn't stab him in the head? Surely he knew by that time that anyone who dies comes back? And when Rick was outside and they heard gunshots, that was them shooting the guy who'd been strangled right? But surely it should have been one shot to the head since everyone is able to do that in the show?
The other thing was maybe it was the guy Rick killed, but I don't see why he would have turned so quickly.
It was absolute garbage how the scientist shot the truck. I knew the writers were desperate for a way to remove the truck from the plot and that's the best they could come up with. There is no way a guy would not know how to fire an automatic weapon after over a year into the zombie apocalypse.