Ok this is where the movie lost me:
in his analysis of the creatures Nevell notes that all shreds of their humanty was completely gone. However, once he trapped the female, the creature that screamed in the sunlight reacted as if she was important to him and this is the reason they set up the booby trap for Nevell.
So, we now have a creature displaying emotional attachement to a female, wanted vengenance for her loss, and set up a trap with a mannequin that Nevell spoke with at a store entrance in the same manner the female was trapped. This makes you realize that the creatures had emotion and some ability to reason.
The movie never adressed this plot arc. IMO, if Nevell questioned this and began to search them out to find answers the movie could have been more interesting and had more action as he started to do some zombie hunting.
Yeah, it just a movie, I know but the unrealized potential of th story bothers me.