At first, he didn't even notice Casey coming up to him. Kylo was focused more on the fact that this wasn't Starkiller Base, that he couldn't reach out and feel the Force as easily as breathing was to him--or as it was to breathe normally, the pain making it more difficult for him to do something that simple. To be frank, he was terrified and he couldn't focus on anything outside of himself right now.

I'm scared. Grandfather, what should I do?

But that lack of focus couldn't last long once he saw movement. Hand reaching out, Kylo grabbed Casey by the throat by instinct, an immediate response to an unknown in his space while injured. "What are you doing?" He hissed the words out, deep and emotions controlled despite the turmoil he felt inside of himself. "Are you of the Resistance, thinking you can take me as a prisoner despite my state?"