I'm guessing it is Michonne. Going off the theory that it's the same person's POV throughout the episode, and that person was in the van and brought out AFTER the rest of the group arrived, it is either Daryl, Glenn, Rosita or Michonne. Based on the view when Dwight opens the doors, you can see the top of someone's head which would eliminate Daryl (in front and the first to be removed). The next person to be removed was Rosita and there was nobody in front of her so she is safe
. That leaves either Glenn or Michonne. When the door opens, it looks like the head in front of our victim is very close to the wall of the camper which would make that person Daryl and the person behind him was Michonne,