[Sorry for my long-winded brain process... XD]
As someone who write panic attacks, experiences panic attacks, and has worked in a psych hospital, panic attacks can be tricky to execute for a lot of reasons--mostly, I've found, because how the panic attack is perceived by the person watching or experiencing it can be vastly different. I've mostly written scenes from the PoV of someone /having/ the panic attack as opposed to watching one, but my beta reader--who has never had a panic attack--was very... unsympathetic... to the way I had initially written it because she /needed/ the 'logic' behind the emotions and thoughts of the person because without that, it just seemed like an out-of-character moment. I ended up having to illustrate/exaggerate the scene in a different way than I would explain panic attacks /literally/ to properly convey the scene itself.
Writing from the PoV of someone watching this will be different. The person having the panic attack will appear to make themselves as small as possible or be entirely irrational about the [current] situation--depending on the person and the type of panic attacks they get, they can even be violent. A lot of the reaction will depend on the person watching it. Have they seen this before? Have they experienced this before? Most people don't actually know how to handle a person having panic attacks. And then there is how does the person having the panic attack react to the attempts to de-escalate the situation?
I think visually, illustrating it from the witness's perspective in this case will be a much more mundane kind of scene no matter what you do because the witness's perspective is free of 'demons.' Whether you are drawing or narrating a scene like this, I think the key is going to be in the thought and emotional process in the perspective character (illustrated or described, depending on the medium) because 'time' itself tends to be more key in these situations than outright reactions. Sometimes, it would take a whole hour for my patients to even be communicative enough to /do/ breathing exercises, so I would just sit with them and do what I could for them, depending on the person. It's hard to watch, and the less you've experienced it, the less you understand it.
Iiiiii don't know if that helps, but XD.
