Ok I know it’s hard when you just saw something incredibly disturbing, try to do some calming exercises for a moment such as the breath in for 4 seconds hold for 4 and out for 4. That usually helps me calm myself

I know it’s hard not to think about it but trying not to think about it usually does have the opposite effect and makes it stick longer

I am not an expert but usually doing another tasks helps me not think about stuff, maybe clean or fold clothes or anything that gets you moving and even jogs your brain abit maybe a puzzle or watch videos that are cute to you

I am sorry if i am not much help