[spoiler]It's debatable if Tim is indeed dead or if he's merely unconscious from the stress and exhaustion of... all that. Also assuming ToTheArk wasn't Alex, that's a possibility. Also people elsewhere have been commenting as to Alex's final words
"If there's someone left, you have to kill them and then yourself" so someone from previous could still be out there, or maybe some third party recovered the camera... time will tell, or the movie.[/spoiler]