"This is no place for you to be right now." Yes, he is hardly in any position that would allow him to tell Prim what to do. Doesn't stop him from going for it. He has a deeply ingrained need to protect, and Prim is in desperate need of someone to look over her. "You need to get out of here."

When Prim doesn't move, when it becomes very clear that she's still going to try and help the innocent bystanders, Jack is a little taken aback. Brave girl. He was not expecting that. Very brave girl.

Of course, brave does not mean resilient, and when another pipe wielding crazy recognizes that Prim is both a special and a sitting duck, Jack has about half a second to react. No way to get her out of the way without putting her into the path of some other dangerous maniac. Shit. There's a grimace on his face as he pulls her in close to his chest and then crouches down over her, grunting through clenched teeth as the pipe comes down on his shoulder.