I'm sorry and truly heartbroken to hear this story since I empathize with you and the families involved.
I don't like sharing my whoes on the internet I mean so many people have worst stories than mine but I lost my big brother, Michael, in a car accident about a week before his birthday and right before the holidays about 9 years ago. It's still hard even now sometimes for my family. The accident wasn't close to home so there was no memorial to visit. He and 3 other people lost their lives in that accident, the one survivor was in the hospital for awhile and didn't remember the accident. I kinda repressed most of the details at this point really though but I know what they are all going through and I tell you it's not easy.
My thoughts and sympathies are with you and the families of the deceased and also to those of the lone survivor and hope they are able to make it.