I have had that same event. It was like somebody slammed a door inside my head with a bit of lightening added to it. It has happened a few times over a couple decades. It has never repeated in a close time interval.

It can be scary but if there are no other symptoms like muscle weakness on one side or extreme head ache, I doubt there is any reason for concern. You may call his doctor to report this event just to get some confirmation.

My best to you both.