Sharing Our Innermost Thoughts

Hi, I’m new here, recently an incident occurred which has left me distressed. A few weeks back my sister-in-law “tried to” kill my parents. Thankfully they are alive because she didn’t have that much guts to do so. All the arguments were happening verbally until that incident. She even dared to call the police and give false statements acting all innocent. But i didn’t have any evidence to prove her wrong. My brother says that all this is among them and that, this shouldn’t affect our relationship as siblings. I feel guilty because I was not in that place where all these took place. But I also feel angry because my brother did nothing when all this was happening. What should I do? I have trouble sleeping and keep getting flashbacks from time to time.