She was dying.
She knew her sins would catch up to her one day. She had doomed herself to a sinners life the day she had made her first kill. They all praised her and admired her because she was a prodigy. Nurtured her growth, encouraged her to train more while boasting about what a great shinobi she would be.
Then they started to talk about a coup. After the Kyuubi attacked the village everybody immediately began the blame the Uchiha for it. After tensions ran too high the elders began to plot and start to rebel. When Shisui unlocked his Mangekyou Sharingan I thought we could the coup and persuade the elders to forget the coup. Then Danzo stole Shisui's eye and ordered me to slaughter the entire clan with the exception of Sasuke.
I actively seek death. Perhaps if I had begged Danzo to spare the children I wouldn't be like this right now. Why was Sasuke the only one he would let me spare? There we babies, innocent children, people who weren't aware of the coup. Why didn't he spare them? Izumi opposed the coup, Akira, Yukiro, so many Uchiha opposed the Coup. Why didn't he let me spare them? Sasuke will kill me before I die of my illness unaware of what happened that bloody night. I wouldn't really care anyways. I am a sinner and I deserve to die.