He looks back at the cat and tries to focus on her when Reyes puts that mask back on. Scratches behind her ears, underneath her chin, listens to the soft purr as she draws closer and starts to settle on his lap. It's an offer he knows that Reyes- that Reaper won't take. And when at one time he would have thought nothing of it, now it almost wounds him. Reyes died, he said, even though McCree could see so much of him still behind that mask. In his actions, in his voice. In the small things, like cleaning out his arm or caring for this cat.

Could still see his old boss underneath all that darkness, and he doesn't want to leave him behind again. He doesn't want to run again.

"... He's still alive under that mask and you and I both know it." He looks up at him again, stares death straight in the face. This is something he doesn't want to back down from.
"I ain't leaving him behind again." It might take time. And Reyes probably won't agree to it instantly- he's stubborn, the damn fool. But McCree makes a promise to himself. As long as he's here, McCree will be doing his best to not leave the man behind. Jack be damned. Overwatch be damned.

He's got to repent for all the mistakes he's made. And he's going to start now.