It’s a nasty thing to see, no doubt.
Things like this get to people in different ways. I had a mate who ran a bloke over in the dark and killed him. He wasn’t speeding, he was 100% legal, and the man he hit was drunk. The cops helped him, the victims family said he wasn’t to blame, but it affected him really badly for many years, and as far as I know it still does, although I’ve not seen him in years
I also know a lorry driver who hit a woman thet stepped out in front of him in town. He was going very slowly, but she fell and hit her head which killed her, but it hardly bothered him.
It sounds like you’re both somehere in between, and I think I would be the same as you, if that helps? As above, get some councilling, try and talk to the family, the cops, the doctor. Don’t try and push it away.