What you describe is an unclear symptom which could be part of a reaction
or could be part of a normal bodily response to the vaccine since the
body needs to think that it has an infection to form the needed
antibodies.  The thing to do is to call the treating vet and likely have
a vet appointment for a follow-up unless other factors the vet will ask
you about ease the vet's mind.  If you need an emergency appointment then
you just plain need an emergency appointment; there is no substitute for
that or for hands on vet care.
 
>but he died only 5 minutes after having the anesthesia gas, isoflurane,
 
It is extremely rare, but yes, we had one do a similar thing but were
lucky enough that they could start her up again.  The trick was that she
needed surgery again afterward and it was touch and go, though she made
it.  There can be a number a reasons for having problems with anesthesia
(also true for people).  Luckily for the gases with ferrets the risk is
low.  I am sorry that he and you had to experience the rare worst case
scenario.
[Posted in FML issue 4023]