Aizawa is a professional hero, he had invaded a house where a couple of dangerous villains lived, he was just going to arrest the villains but they tried to kill Aizawa so in self-defense Aizawa killed them both, when he was almost leaving the house he saw you in your crib, you and a 1 week old baby

Aizawa: It's just a little baby....

Aizawa picked you up