Disclaimer: I do not own Naruto
Sakura hears of the massacre from the Okiya Mother. Her eyes go wide and she thinks of the nice, but kind of stuck up, Uchiha kids in her class and of the little brother of their killer.
The other kids in her class don't understand and she curses the stupid Hokage for trying to keep it under wraps.
That is what causes evil.
She watches as the girls in her class pout over the fact that Sasuke is not in class and she cannot contain her disgust at their superficial behavior.
"How?" She asks Akiko one night and the woman sighs.
"Because they are young and do not understand loss and sacrifice like we do."
Sakura curls up around Akiko and decides that she will help Sasuke get rid of those stupid people.