Annie just betrayed the scouts by taking off Marco's ODM gear and pushing him. Three people are staring at Marco getting eaten by a titan; Annie, Reiner, and Berthold.. you saw the whole thing.. they took off his ODM gear so he would be eaten! Annie, Berthold, and Reiner act sad. Luckily, they haven't noticed you yet.

(Annie): She looks sad outside, but inside she's happy that the plan is working

(Reiner): He looks all sad but if you look close enough there's a small smile on his face.

(Berthold): He actually feels a bit of guilt but hides it and looks sad

(Marco): Screaming, not wanting to die and wanting to be saved