what was the awful thing?
Ask yourself, was it really that awful? Then, ask him why he did it?
If he was your best friend, though you should know that he did it and not need to find out over FB...unless it was murder, but then it shouldn't be posted about.
As for advice...you need to let him know that divorce is normal nowadays...it's just like a legal break-up...that's all and people change...sometimes they change so much they aren't compatible anymore. But what he needs to realize is why aren't they compatible...was it correctable? if so, who stopped working? why did they stop working? when? etc.
These things need to be identified and addressed and corrected. Otherwise, he will experience many relationships like that.