That sounds really hard. My first thought was depression or another medical issue.
I don't want to mess up your NC, but if the opportunity comes up to suggest a medical checkup to someone who does have contact with him, I might suggest that.
My husband is doing a much less extreme (so far) version of this, and I suspect depression and a mid-life crisis are contributing factors.
Me: 44 H: 44 Kids: 20, 16, 16, and 10 Together/Married: 22 years H announced he was emotionally detached and considering D: 4/4/16 H announced he is going to try to stay and reconnect: 5/1/16