Wife trouble

My best Frnd and his wife had delivered a boy last year. These days my mate has been very upset and so upon confronting him he shared his wife's been very abusive and difficult to deal with in the last couple of months. She has been taking out all of her post partum depression and frustration of motherhood on my Frnd by showing anger and in fact even using violence. She throws stuff at him and damages household and personal property. He asked me what he should do cause he feels very insulted and pissed off when she does that at the same time feeling bad for her. But I don't think it's the right thing for his wife to do this? What do you guys think? Looking ahead for your advice so I could get a third opinion and inform him the right thing to do. Thanks all