Not to be a downer or anything, but does anyone know the procedure for what to do if you think one of your neighbors may have died?

My building has a lot of really ancient people in it. One guy, down on the 3rd floor, has been looking worse and worse over the last couple of weeks. Hard to really tell, since he avoids talking to me or anyone else, but I run into him a lot on the stairs since it takes him half an hour to get up or down them.

I haven’t seen him in the past few days. The last time I saw him he was breathing really, really, really hard while going up the stairs. I asked him if he needed help and he ignored me as usual. I actually waited a landing above his to make sure he got to his room alright, but his breathing sounded just terrible. Now I haven’t seen him in a few days. Maybe he got himself to the hospital, but I just somehow doubt it.

Should I call the landlord? The cops? Someone else?