I don't get where that whole army of walkers came from. My understanding of the farm was that it's completely encircled by a fence, far enough from the house and other places that walkers wouldn't be attracted by sight or sound. (This was the fence we actually saw them checking this very episode.) Yes, gunshots and the like would be enough to attract them, but the group doesn't fire guns that
often. If a walker happened to come upon the fence, or was attracted by gunfire, he'd shamble around it for a while and eventually leave. The watcher on the RV was just in case one of them happened to get through the fence.
Now we see there's a whole army of walkers ready to converge on the place?? Yes, they were attracted by the shots, but they were already right there and practically within sight of the house! Is the place not as secure as I thought?
And Shane sure reanimated fast compared to Amy.