Moving Johnny's clothing out of the way, Cas wished he had a decent light to get a look, but the monochrome settings of their surroundings would make it difficult to see anyway. Nevertheless, he pulled out his lighter and flicked it open, shining it in to see if the bullet could be seen. There was a clean wound, moving through his body. That...was either very comforting or not at all, depending on Johnny's ability to withstand.
"He's been shot," he replied bluntly. "Generally, I would say we need to get him to a hospital. Regardless, we do not have that option right now. So we're going to do what we always do in this situation. Unless of course you've never treated a bullet wound in combat before."
He didn't exactly have the time to explain, so he hoped Rob was aware. As for Dean, Cas was depending on him not to get the rest of them shot.