Johnny looked back at Rob. He was not happy. It wasn't that he didn't think Rob could take care of himself. But he didn't want to have to keep an eye out for himself, Mary, and another person while the killer was still an unknown quantity.
And he thought maybe Max could do with a little help.
"If you're coming, stay the fuck back, okay." There was no way that Johnny was leaving the matter up to debate. "You watch out for yourself, but you watch my back too. Let me clear the rooms before you go running in there. When we find Mary, you're going to have to be really alert. I'll get her free, make sure she's okay. You ... just stay back."
He also might have wanted a moment in which he could have a few quiet words with her. Something that he didn't want overheard. Or maybe she would. He didn't know right then. But having the option was good.