Everyone grieves in different ways, similair to surgery reacting to everyone differently.
Just be available for your son to talk to you.. He will when he is ready...
Remember there are 5 stages of grieving...
denial, anger, bargaining, depression and then acceptence.
In the denial stage we refuse to believe what has happened. We try in our mind to tell ourselves that life is as it was before our loss. We can even make believe to an extent by re enacting rituals that we used to go through with our loved one. Making an extra cup of tea for our loved one who is no longer there, rushing back to tell someone that you have met an old friend. Flashing back to times and conversations in the past as though they are here with us now. Introducing someone accidentally by your loved ones name to someone else. They can all be part of this stage.
We get angry. The anger can manifest itself in many ways. We can blame others for our loss. We can become easily agitated having emotional outbursts. We can even become angry with ourselves. Care must be taken here not to turn this anger inwards. Release of this anger is a far better way to cope with grief in my experience.
Bargaining can be with ourselves or if you are religious with your god. Often we will offer something to try to take away the reality of what has happened. We may try to make a deal, to have our loved one back as they were before the tragic event occurred. It is only human to want thing as they were before.
Depression is a very likely outcome for all people that grieve for a loss. This is what I would consider the most difficult stage of the five to deal with. There can be a the feeling listlessness and tiredness. You may be bursting helplessly into tears. Feeling like there is no purpose to life any more. Feeling guilty, like everything is your own fault. You may find you feel like you are being punished. Pleasure and joy can be difficult to achieve even from things and activities which you have always gained delight. There can even be thoughts of suicide. There are many different ways in which this stage of grief can manifest itself. If you at any time in this stage feel like doing yourself any harm please do seek professional counseling. Self preservation is a must.
The final stage of grief. It is when you realize that life has to go on. You may still have thoughts of your loved one, but less intense and less frequent. You can here accept your loss. You should now be able to regain your energy and goals for the future. It may take some time to get here but you will.
In children it is said to watch for these signs ...
COMMON REACTIONS TO GRIEF/LOSS
Making adjustments for the age and development of your child, think about the behaviors you have noticed in your youngster. The following behaviors are considered fairly normal reactions to a loss. Depression/anxiety
Poor school performance
Acting out anger in inappropriate ways
Regression to an earlier developmental stage
difficulty parting from parent
Eating problems (e.g., lack of appetite)
Various physical complaints
stomach aches, tension
inability to cry (may complain of "sore throat")
You may want to read the entire site on children and grieving so here is the link