Coworker in my department has been through a divorce last year and unfortunately it changed his personality so much that he started acting like a complete a**hole (for the lack of a better word, sorry) towards pretty much everyone in the office.
He's been here for at least 5 years and he always used to be strongly opinionated and never shy to push his views hard. But ever since the divorce this reached a whole new level - he's terribly sarcastic, ironic, refuses to train up junior staff members, gets into arguments with anyone who dares to disagree with him, and so on. More often than not he comments and is highly critical on personal level (think of "you are stupid" rather than "what you propose is stupid").
Last year the team was quite ready to put up with that and cut him some slack as we knew he was going through a rough patch. But here we are a year later and he's not getting any better. Quite the opposite.
I am one of few people over here who he kind of respects to some extent because we've known each other for years since we used to work together in one of our previous jobs. And I can see over the last year how it all goes downhill for him. I know that most people over here try to avoid him, and quite understandably so. Our manager tends to give him one-man jobs where he doesn't have to team up with others to avoid conflicts, and so on.
I told him not to be so verbally aggressive towards others, or try to be a little less sarcastic for start. I told him he's not helping himself when acting like this. And I'm afraid that after his marriage fell apart he's ruining his career too - the next time someone will have to go I bet he'll be on the top of the list. And with this attitude and in his age (early 50s) it will be hard to find a new job. He may just as well be ruining the rest of his life now.
He may need a professional help but his ego will never accept that it's him who's got the problem, not everyone around. I would like to gently help him get back on track but don't know how. Also it's hard when the rest of the team over here have given up and simply avoids him.