This is a dreadful thing that has happened; such a huge shock will naturally take time for you to come to terms with it so don't try to make sense of it at present; just live day to day. All you can do at the moment is try to create a centre of stability for your grandchildren, and your daughter in law if this is applicable.
Contact your friends by text or email, thanking them for their support and saying truthfully that you are quite unable to talk to people at present. At least the news is out so you don't have to tell people, and you will be surprised by how kind most people are.
A similar thing happened to a friend recently, involving her son-in-law, of whom she was very fond. The police were kind and offered practical help, social services less so. The family went to ground initially, but later she bravely visited friends to explain personally what had happened, thus diffusing unpleasant speculation,as the court case was not publicised. She was completely truthful at all times, not excusing his behaviour, but supporting him as far as she was able, and played a huge part in helping with the grandchildren. Two years later the family is emerging into a different, but more settled life. The son-in law is back in work following his prison sentence.
Also, have you seen your doctor? They can offer short term practical medication and contacts for support; you need to look after your health.