I don't think it was necessarily a 'panic response', (though it could have been), but just a quick reaction suddenly coming into clouds and instantly looking to get clear.

I was never certified IFR, but I did take a few lessons. It's really amazing how quickly you can be engulfed in clouds, fog, and lose all visual reference. I don't remember this well but the correct response in that situation, (unless you're flying IFR), is to do a 180 and descend... this sounds much like that.

All of this, however, is leading to a bigger question.. why left if he knew the mountains were there?