Coworker giving everyone the silent treatment

[Happyfuture]

I work with 2 women and a guy in a retail setting in a small shop. The last 6 months the guy has been giving people the silent treatment when in more than a team of 2 for what seems like the smallest slights (being told to do something that is needed for the job and refusing to do it, arguing with the manager over small issues like pricing which she has no control of).
He starts the day in a great mood, but hes all about himself and will only talk about what he's up to/wants to do/ been up to, and after an hour or so he will suddenly give everyone the silent treatment. He will ignore you if you ask him something work related, wont chat, and will bang around loudly slamming doors and being aggressive. When confronted as to why he is doing it he refuses to give a reason and tells us all to ignore him. Its getting worse and is becoming emotionally draining as we are spending over 8 hours a day together.
Its becoming increasingly aggressive when he's quiet he makes swift darting movements, standing in corners of the shop like a statue wringing his hands, angry facial expressions, the banging of doors and cupboards is getting worse and sometimes we are concerned for our safety as we worry about this behaviour, but he just won't talk about it. The managers taken him aside and asked whats wrong how she can help and he will not give a reply.
Our concern is some days we have to work 1 to 1 with him and as of yet it hasn't been the same on those days (he's usually nice 1 to 1 and chatty all day with all 3 of us) as it is with more than 2 people, but we worry this will start happening on those 1 2 1 days. Its affecting our mental health alot and we try to ignore it but its not helping at all. What do we do?? How do we help resolve this? We are a super friendly team and we really care for each other and we are at a loss as what to do to either help him or get him to stop this behaviour.

To be honest, he sounds ill. I think your manager should be arranging an occupational health referral, if there is such a thing for your workplace. But in the end this is for the managers to resolve. He doesn't get the luxury of refusing to reply to a manager. The standards of behaviour should be set for him, and he complies or there are consequences.

You and colleagues need to speak to manager and tell them it's really effecting you.

Until it's sorted, I think you all just need to be the bare minimum polite with him but no more, don't be super friendly to people like this, their ego feeds off it.

Imagine being married to him!

Thank you, I do think its a mental health issue but when he's refusing to speak with management about it there's nothing that can be done.

Manager knows how this is affecting us and she has contacted the area manager but it seems to have fallen on deaf ears. I wont ask him whats wrong because he's already told me not to ask him as he's fine
Everyday is like a game of Russian roulette as we just don't know which version of him we are going to get

I'd approach the manager as a team and tell them that either they sort out this man's behavior or you'll all put in a grievance to HR. That might do the trick, as they know you mean business and it will reflect very poorly on your area manager and manager if this gets out. If it doesn't work out, put in a grievance. His behaviour is totally unacceptable.

All you can do is keep raising it with your manager. If you and others do it often enough they'll have to go something. If nothing is done, can you write a letter/email to the area manager as a team outlining the issues, offering examples and asking why nothing has been done to date and that you'd like a meeting to discuss how they're planning on dealing with it - cc in their higher ups if need be too.