I expect there are a lot of us at the moment that are often on the brink of a meltdown. But we aren't 6, and have the emotional experience that tells us how to get ourselves under control and not bite a passerby.
His dad sounds amazing and knew just what to do. I agree with the advice on here, and think you need to look at the run up to the tantrum. Were there signs that he was getting frustrated, and could you have done anything to head it off.
We have been looking after our 5 year old GS since schools closed, and although no tantrums, there are definitely times when he
' goes past himself' as my mum used to say. We have a corner with cushions, soft toys and a crochet blanket, where he can go and snuggle up, even punch poor old bagpuss if he feels like it. His place, his terms, somewhere he feels safe and maybe designed himself.
I remember seeing a chill out tent once in a primary school , which they said worked for some of their pupils. Teachers were keen to use it too, but had a comfy corner in the staff room.