Getting over the image of this kitten's death?

That's so horrible but it wasn't in any way your fault-it was just an accident but if anyone's actions contributed towards it then it was your neighbour for starting his car knowing there may be a kitten under it. The images in your mind will fade with time,but it will take a while to get over something so traumatic so just take it a day at a time. Is there a local cat rescue group that helps with feral cats? you could contact them and offer to help and I'm sure they will be willing to help with the two females and it may help you feel better too.