Yeah, the narrator does seem both innocent and not. ^^
Thank you! I really wanted to emphasize how mundane, in a way, dealing with a dead body became (oh, just help me move this and stop being so upset, will you?), how mentally fatigued they were because of all the events, and I'm happy to see it came forth.

I actually wanted to play more with that line, add some more to it, but am actually happy I didn't. It says just enough, and leaves just enough to the reader. :P

There could very much be more than one killer. Pointing fingers only creates more chaos because you can't prove anything... But if you kill the person you believe is the killer... well, you might have solved the problem. And you might've not.
I somewhat wanted to write it a way that the killer would be known to the reader, but not to any of the characters, even the killer himself, and have him suffer a mental disease, but I believe this strikes much closer to home, so I went down this route instead. :p

Yes! Which only adds to the entire mental stress of the occupants in bunker because they're constantly left wondering who it could be, rethinking all the memories they have together. I imagined it like someone sitting in the corner, watching their neighbors as they passed by and thinking of them: "Could it be him? But the way he handles meat three years ago at his barbecue party... I don't think so... But he was very bad with his dog and not a single neighborhood animal liked him. Tracy, maybe? She's always been kind of shy and lonely, and just weird in general. Oh, Bill! He's the tough guy type. He's got a skull tattoo on his right shoulder and has always been around those shady bikers...." and so on, and so on...
Maybe I should've put in more of this. :P

Yep. No higher motive. Just killing for the sake of killing. The very worst kind.