This is Eren a short while after he spoke with Armin and Mikasa in chapter 116 - telling Armin he was weak and Mikasa that he hated her. Look at his face. He looks broken. Gabi literally has to say 'hey...' as though he's lost in thought and she needs him to snap out of it to listen to her before she asks about Falco.
What do you think he's thinking? Does he regret what he did? Did he think there was no other way? Is he thinking that they won't forgive him?