I didn't see it happen, so I can only guess based on the snippets of words exchanged. But it appears that he and his mate climbed up a short, rocky section from the beach, up into the trees - I assume to pee - and then, as they were climbing down again, one of them slipped and hit his head pretty hard.
I plan to call the hospital tomorrow after they've had some time to do surgery, etc and just check how it went - if they'll give me any info. But he was in good enough condition when I said goodbye that I'm confident he'll live and I really don't think he'll have any brain damage based on how he was able to communicate with me and the guy doing all the practical first aid stuff.
He'll probably have a heck of a scar on his forehead, and he's sure as hell going to be more cautious in the outdoors moving forward. But I do think he's going to be okay.
Thank goodness. Made for quite the day for you. Lucky you were around.