One thing I learnt - ignoring how you are feeling and shutting out what's in your head is never going to end well. You need to say what's in your head as your feeling are just as important and valid.

I started with focusing on the basics - making sure he's eating and drinking. Whenever I got a drink, I got one for him - whether he drank it or not, the same with food.
Talk to him. Tell him that you want to do what you can to help, but you don't know what to do to help.

Is he on meds?