Freedame,
That would give anyone Post-Traumatic Stress Disorder.
Adults can acquire it as a result of a traffic accident, not just warfare.
Being witness to something so CRUEL and violent (with your ears) is deeply damaging.
So please, don't give up on yourself or decide you "just have to live with this".
You do not!
Have you had counseling, and if so, have you had enough of the right kind?
Your life can heal enormously, your mental health can become strong, your emotions can become a normal range.
But imo, you need and deserve specialized long-term counseling with a therapist who specializes in PTSD.
It really helps to interview several therapists until you get one you sense is just right--someone who understands trauma.
A domestic abuse shelter or hotline would be a good place to start. Violence is violence. A rape crisis center. A Veterans' hotline, for references.
Never belittle that memory--it is enough to give you PTSD. At the same time, that memory might in some way become a key to your healing.
Is there some work, even volunteer, that you might like to do with unwanted animals? Perhaps that would be another branch of your healing stream.
Hops