"Where's Jeremiah?" (spoiler)
Firstly, the movie seems to imply that Jeremiah (neighbor guy) and Sam were "involved" to some extent, in the few days following disaster and them moving to his (?) cabin. Seriously, Sam and the Jeremiah were out in the woods sitting/talking around a fire, without Will, at night, while he was sleeping? That was weird. Then later, Jeremiah says something like, "I saved her life, we have a bond, we thought you were dead." That could've just been him lying to Will, or trying to upset him, but what would be the point of doing that if he was planning on shooting Will in a few seconds anyway? It just seemed like the movie was trying to tell us that they'd been involved after assuming Will for dead.
So after Will killed him, I was particularly confused at this exchange:
Will: We have to go right now!
Sam: What? Go where? Where's Jeremiah?
Will: He tried to kill me. Come on we have to go.
Sam: What? Okay.
*queue next (and final) scene*
Really? So she wasn't interested in what happened? Just, no questions asked, OK cool let's go? Now, even if they hadn't been involved, it was still apparent that ONLY Will was suspicious of Jeremiah during the campfire talk. Sam seemed indifferent. So even if nothing happened between Sam/Jeremiah, it's still very strange that she didn't ask what happened while they were driving off.
(While I'm at it, other things about that whole final scene were super weird. Jeremiah says something like, "I've seen war game simulations before where they do things like this," and immediately Will gets super aggressive and pissed off with him. What? Jeremiah didn't say anything extreme like, "I'm the only real person here, none of you are real, I must be in a simulation!" but that seems to be how Will took it. I feel like there were missing lines of dialogue here as Will seems to get upset out of nowhere. Of course, Jeremiah does indeed turn out to be a bad guy, but still. I also have no idea why Will chose to abandon his gun at Jeremiah's body, even if it had no bullets left. An empty gun is still useful.)
It really feels like they rushed the ending, but otherwise it was alright.