What happens when you are in a stress induced state? What about if you might be driving down a busy freeway with a large traffic jam? Enclosed into a small place like a train or plane? This happens to many worldwide and for most some are not willing to accept or acknowledge that they are in fact having a panic attack. It can be something quick with a few quick races of the heartbeat or something more intense where the person is suffering from hot flashes and a fear that could almost paralyze a person.
This can happen it the blink of an eye and within any real warning signs. For some people who have never had an episode like this before they have no idea what is going on which of course intensifies the episode and draws it out. It can pass by quickly or last as long as the fear keeps hold of the person. This can be the same with anxious children.
A psychological tick like a mindset can be a trigger; a small emotional issue that can quickly heat up leading to a new panic for the person can set it off.  For some people it can be something as simple as driving too far away from their home; their conform zone. It could start with feelings of dizziness and leading up to nausea or even to the point of thinking everything is too overwhelming (with the fear of imitate death).
A panic disorder cannot be prevented but it can be handled within a controlled manner. Being prepared and knowledgeable with what is happening to you can be play a large part in being about to reduce the anxiety that comes along with it.