[lee martell]

This actor has always held a strangely blank facial expression, no matter what the situation is around him.
As though the situation was happening to somebody else.

This may simply mean he was nervous, or perhaps that he is used to masking over any real emotions stirring up from within. If, indeed, he looked ‘stunned’ as the verdict was read, that info must have finally broke through the armor of neutrality.

[x]

If he's always had a "strangely blank" facial impression, maybe the "stunned" look on his face was was the same look he always has. Possibly his eyebrows went up, but there may not be much difference.

The photo is from a charity auction: "Meet Danny Masterson & Enjoy a Walk on Role on Netflix's The Ranch." The auction has been cancelled.