When Grisha Yeager and his little sister Fay wandered outside of their Liberio Internment Zone without an exit permit to see a blimp, Gross and his fellow soldier were slacking off by the riverside and they spotted and caught them. Kruger delivered physical punishment to Grisha while Gross walked away with Fay. However, her mutilated body was found the next day in the river and Gross, accompanied with Kruger went to the Yeagers' house and informed them of the death of their daughter. Gross claimed that he took Fay to the border of Liberio and that it was her own fault for wandering around town without permission to begin with. He later revealed to Grisha that it was education when he fed his little sister to his sons' dogs and thanks to that, they grew up to be fine young men.
Kruger pushes Gross off the Utopia wall, the Titan he just turned for Grisha, grabbed him and started eating at his face and he is killed.
