It's the difference between drugs and poison, literally the same.
Some mushrooms have psychedelic properties, others just contain poison that will kill you. Pro tip don't eat the poisonous ones, they all look very similar, although I think death caps actually do warn you by being giant and red, but this sounds like a murder rather than accident.
Mushrooms in general are one of those things you should stay away from unless you are 100% certain you know what you are doing.