If something leaves you stupefied it has made you so astonished you can't speak or even really think. When your husband backs over your foot, and then drives back over it trying to get out of the way, and in the process hits the front of the house, you might feel stupefied.
Stupefied and stupid share a root, but they've come to have slightly different senses. You might call someone stupid if he generally doesn't think well, but when someone is stupefied, that's more like becoming temporarily unable to think. This could be a reaction of astonishment, fear, confusion, or drugs. Opium will make you stupefied, and TV marathons of reality shows might do the same.