I only knew of convulsions due to epilepsy, but apparently there are other causes. I had to look up the definition, which seems to bullseye the observation: "(of a person) suffer violent involuntary contraction of the muscles, producing contortion of the body or limbs"

Now put that together with the fact that others raise, that no medical folks were concerned, and we have a mystery here. VictoryTurkey mentions panic attack, and while panic attack descriptions don't seem to mention convulsing, they do mention "abdominal cramping", which perhaps is what we saw??? Just another tragedy and head-shaker to add to the story yesterday.