"Well let's get the hell outta Dodge before we see what it can do!" McCree figures a creature like this probably gets by underground by feeling vibrations, so he doesn't know if shooting it in the eyes will help, but it's worth a try. Turning back, he lines up a shot, but just as he's about to pull the trigger, the creature looks right at him.

And that's all it takes. Immediately, McCree's entire form turns to stone, arm still outstretched to fire his gun. And while he doesn't know what's happened to him, he knows it's bad. He can't see anymore, or even move. He tries to shout, but can't. In fact, the only thing he can do is listen.