As much as I feel for the guy, at the end of the day its clearly not safe to have someone like himself working on an aircraft. What if he suddenly decides to end it all and take everyone with him. He does have access to a flightdeck and he could easily wander in and grab the jemmy. Slightly sensationalist but worse things have happened.
The company should really be taking him in hand and ground him immediately (it may not be the best thing immediately for him but in the long run it may very well help) and find him some support and assistance.
BA has a service called Crew Care where by if we feel the world is getting on top of us we can call this number which is manned by crew volunteers and they will do their best to help you. I have also (and some have questioned whether I should have done this or not but I felt it was right) had a quiet word with someones manager as I was concerned about their condition. This persons manager took control of the situation and six months later I had this colleague come up to me at work and thank me.
I think the worst thing anyone can do is just ignore it but its also not nice to have to get involved.