"John... Doe." Jack has spent enough time in America to know that's not a real name. It's the kind of name people give bodies that nobody can identify. Why would anyone name their child that? Poor guy!

Unless he's hiding his real name, which is possible, but also not something Jack is going to judge him for.

So he shakes John's hand as warmly as he can, tucking the first aid kit under his arm so he can use both hands for a moment. Yes, John's other hand gets a curious look, but it's not a wary look. Just kind of interested. "You're sure you're not hurt? That doesn't hurt?" He nods at the left hand.