Check this out!

[Stefan-A]

I can think of two far more likely explanations:
- He feels a squeeze and attributes it to the snake, when it is in fact a symptom of an impending seizure.
- The snake is indeed squeezing and he has a psychosomatic reaction to it. He essentially triggers the seizure himself.

Frankly, the simplest explanation is that one of the thousands of times the snake has happened to squeeze, the guy has had a seizure and now he thinks that there's a correlation.