There really isn’t anything that one can say at a time like that.
It is best just to be there for them to LISTEN to what THEY have to say, and to help in any way you can. Telling over some of the stories and ideas mentioned above, while the intentions are certainly very good, is unlikely to be helpful when the loss is still so new and so intense.
May HaSh-m be menachaiym them through this painful nisayon.