Hello Harbourlight42, I am so sorry to hear about this. I have a little insight into a small part of this subject. I am not sure if what I say will help at all but I hope perhaps a little. My son was murdered some years ago in a very brutal, totally unprovoked attack. My other children were young and so in this respect I can only say how we dealt with this situation. The first thing to say is there is no right or wrong way, just your way. Also we found the best thing to do was to be honest and explain everything that happened to their brother in respect to their age. Children are always tougher than we think and I think we were right to be honest, but again you know your own children or grandchildren. I feel that they would have heard or discovered "things" from other people and we wanted them to know "stuff" from us. One of my children was 8yrs at the time and although extremely upset, distraught even at times, they were a lot stronger than I was at times I think. It was on the television and in the papers and so they had that to deal with as well.
I suppose I am just saying, go with your gut instincts in how you deal with this and you will find that your grandchild is probably tougher than you think and if you use language they understand t will be ok. Also it is surprising how quickly children "get over" things and deal with them.
I do hope I haven't gone on too much and I sincerely hope things get better and if I can help in any way, please ask or p.m me.