Many shocking facts about Eren and previous events are revealed in Attack on Titan's final season. Carla Jeager's cause of death is one of them, and some fans might even question whether Eren killed his mother.

Even though Eren did not kill his mother directly, but he played a role in Dina Fritz's (the Smiling Titan) finding about his mother (Carla Jaeger).

Eren invited Armin into the Path during the last episode, and the two of them talked about a lot of serious topics. Eren gave an explanation of the thinking and motivation behind his terrible actions, which led to many deaths.

In the end, Eren revealed that he had influenced Dina Fritz to turn her attention to Carla, who was stuck under the collapsed building, in order to save Bertholt from certain death after he leaves his Titan form.

Although Eren did not tell Armin this directly, but he understood what his friend intended to express. As he listened to Eren's words, he could see hus eyes grow wide with terror.

Eren realized that Bertholt had to survive and his mother had to die after acquiring the Founding Titan's strength and knowledge. Also, young Eren needed a reason to join in the Survey Corps, while Armin needed to obtain the Colossal Titan power.

In the end of last episode, Eren accepted that he had an obsession with freedom. Despite his grief at his mother's passing, he saw Carla's death as a necessary sacrifice in order to have the future he wanted.