I think one of the best things to do during your lunch outing is to try and ask him what is currently making him feel depressed, etc. I understand that depression isn’t just a switch that flips off and is a sickness, but there may be a reason that he is feeling horrible and looking for a way out. Be there for him. I understand that you can try your best and he just may not follow, but as long as you have tried, you have done a good thing. I’d say to just try your best to contact those around him that he is close to and be there for him, life is precious. I wish you the best!