They'd all fit into the category of making the guy relive old pain, physical or mental.

The way he snapped and went the knife version of being trigger-happy? [he folds his arms over his chest, trying not to let an uncomfortable look settle for too long on his face. the familiarity is eating away at him. he knows quite a bit about the mentally unhinged.] There has to be more to it than just disgust. Something that drove him to that extreme once the straw broke the camel's back. All I have to do is figure out the best way to tap into that.

...It's the details beyond that that I need more time to think on.