Most of us are all challenged as to how to respond when confronted with someone who is grieving and there are no right words to say. Listening, comforting, supporting no matter whether the feelings are anger, sadness or grief is most helpful. The relationship is more important than the words. Because most of us are uncomfortable with others grieving, we often try to make things better or rush them through. Instead we need to be patient and allow the person to experience the emotions they have in the moment. Just as everyone grieves differently, everyone grieves at a different pace.
Children like adults need permission to grieve. We often ignore grief or try to distract others from grief by keeping them busy. Instead provide an opportunity for the child to talk about the person who died and to develop their memories of them. I often ask children what they will miss about the person who died and many children like to draw pictures to keep of their most cherished memories. Families can also help children develop memories through rituals or through discussing their faith and religious beliefs with them as well.
There are several books available to help children through the grieving process. Here are a couple that I've used: