[Shun flicks his phone on briefly to check the pictures, then puts it away again once he's satisfied he's memorised the face. As long as he can identify the guy when they encounter him, that's all they need.]

Watch him first, then confront him. Getting an idea of how to go about it first would be best, especially since even if the people around him won't notice us, they can still hear him if we corner him somewhere public.

[Unfortunately, the fact that he can't teleport living people doesn't help there.]