Well, Sabby, there are long involved answers here and short not-so-involved answers. If you wanted the long involved answer, my first inclination would be to suggest you check out the videos on YouTube that have been uploaded of talks given by the Buddhist nun Pema Chodron. Pema teaches that such things as anger, depression, etc. are infact our treasure. We can open to them and thus use them to achieve peace and equanimity. Pema has also written numerous books on the subject. But this is a life-long journey and I get the sense that what you're looking for is something to put out the fire, so to speak.

In order to deal with the anger you feel about this sad incident, I would suggest some physical activity, as intensive a level of activity as you are able to engage in even if it's only some long brisk walks. Talking this out with a therapist or trusted friend may also help or writing about your feelings. Perhaps consider writing a letter to this man (not one that you will ever actually send... but just to get your feelings out.) Or you could write the letter to your grandchild or maybe the judge who will be hearing the case. Here again, you won't be actually sending the letter. But writing it, may help to relieve some of the stress you feel. Ideally, you might do a combination of these things. Take a brisk walk to somewhere you enjoy being. Walk until you're tired. Write about your feelings, perhaps in a letter, do some meditation or say some prayers depending on your spiritual leanings, talk about your emotions: anger, fear, feelings of helplessness (if you have them) with a friend. Personally I'm a believer in the idea of attacking something like this from multiple directions more-or-less at the same time. Best wishes!