It's 'incomprehensible' to me that he could have acted that way.
I found his behavior utterly 'incomprehensible'.
an 'incomprehensible' theory/decision
(..) And you yourself, you still have your vigor! And then you find yourself a martyr to distraction by so many women. Forgive me, but I find that incomprehensible. As though, I should leave this restaurant and steal a roll from a baker's shop. Well, you know, a freshly baked roll. (..)2012 Anna Karenina