There are lots of good insights and suggestions here. I feel that, as Flickety says, plenty of physical contact may well calm him and make him feel more secure.
It did occur to me that perhaps in a quiet, settled moment his mum could start chatting to him about anger and what makes people angry. Or, I think there are several books to read to children about coping with anger, which might help to open up a discussion. It might be helpful to find out if there is anything in particular that he is angry or worried about.
Six foot two, eyes of blue. kg v lb. cm v ft + ins
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