Damn, OP. That's disturbing. I would suggest that you tell his parents, just so they know that he's online and doing things like that. Really for his own protection - who knows what kind of information or behaviors he could develop if unsupervised. It's very likely that his caretakers (parents? institution?) don't know that he's sending out messages like this. The delusion canvasses some very violent thoughts and fears and I think you should let someone know about them.
Again, that sucks that your old friend has been reduced to this madness.