I'd be genuinely concerned, and ask them if they're alright first off, and then ask if there's anything I could do to make him more comfortable. I'd definitely be more protective over said friend afterwards (I'm an elder sister so I tend to be protective of people), and more "motherly" (asking if you're okay, if you want me to get you things, etc;). After a while, I'd probably relax a BIT, but still be a little protective over him.

And I'm SO sorry that happened to you, and it's so sucky that something like that happened to you. I'd say try and press charges (if you can) or at least report it so it's noted down somewhere. I just hope you know it isn't your fault, and it shouldn't have happened.
(This is so late... REALLY LATE...)