In extremely high doses, muscarine, the poisonous compound in Amanita Muscaria, can in fact cause death - usually from cardiac or respiratory failure. Typically there are only very small amounts of muscarine in A. Muscaria however.

Muscamol, the psychoactive compound in A. Muscaria, is not poisonous.

For an interesting tale of survival involving the Death Cap's beautiful and deadly sister A. Virosa aka The Destroying Angel, check out this post on the Cornell Mushroom Blog.