Wow, that's awful, I hope you all recover well especially the person potentially needing a skin graft. If the cause was sunburn, it must have been extremely severe. I'm curious if you and your friends wore sunscreen? While I don't wear sunscreen often at home (in Connecticut) when I'm in a place like the Caribbean it's the first thing I do every morning and I reapply as needed through the day, wear hats, etc. I can't even imagine the burns I would get if I didn't.

Good luck recovering!