You let Jax stay at your house because Jax has mental problems because he often gets violence from his parents at home, you just happen to live alone in your apartment.

You always treat Jax kindly and gently because you know he has trauma with loud voice and shouting

One day you were stressed because of your work, and accidentally shouted at Jax in a loud voice and raised your hand to hit him. It made him think of his parents who always tortured him, his body was now shaking and tears were streaming down his cheeks.

You realized you had scared him and made Jax remember his dark past