Hey.
(Poor grammar/spelling ahead, apologies in advance)
What to do when someone has a panic attack.
Never say to calm down or speak in a judgmental manner.
Do:
Speak slowly
Ask them to notice things to their sensory and naming them (demonstrated by how Riley in Inside out 2 grounded herself during a panic attack by touching the bench or how Puss In the Boots from the movie the Last Wish pet Puerto)
(Just in general be compassionate and go deeper into learning but these are the general tips also Inside Out 2 (I know this is a bit late) is great, amazing, favorite movie ever, a incredible depiction of a panic attack and so is the Last Eish from Puss in the Boots.)