I'm not sure what to tell you in this instance as I have not had that experience. But recently we had a similar experience with Shadow our Akita( RB March 7, 2005), and when he snapped out of it he was completely confused and then was ok. Considering the size of this guy and the damage he could do to someone if he was to really get hold of someone we needed to find out what may have happened. We took him to the vet and they ran a battery of test it turned out he had a brain tumor and the pressre it was putting on his brain used to make his kind of go off into another world and he didn't know where he was or who anyone was.

I know this is a worse case sinario but I think your best bet would be to take him to the vet and get some tests done. If it is something serious then maybe you can catch it quickly enough to help him. Let's hope it isn't and that something just spooked him and that's what caused his reaction.