Well, clarifying the problem is always a good start! Yes, I can see better now what’s making it tricky. I guess the same principles still apply: focus on your onlooker’s reactions to what they are witnessing, rather that (just) the action itself. Maybe think about the onlooker experiencing the violence as a series of sounds, movements, colours, feelings etc.
Yes, you’d be very welcome to pick my brain about trauma and trauma triggers. Feel free to DM me or whatever is easiest.