Not sure this is the right place to post this, but I'm a bit desperate for advice and there isn't a dedicated mental health community. Sorry if inappropriate, will delete.
About 10 years ago a friend of mine had what I think was a psychotic break. Or maybe his problems just escalated enough for him to get super hostile and paranoid with me and push me out of his life, and the psychotic break came later. Basically, he got progressively more and more antisocial and paranoid, increasingly incoherent (talking about a lot of far out conspiracy/woo type shit) and just hard to be around. I sometimes called him out/challenged him on this stuff (not with the necessary grace, I'm sure, but I was young and dumb and didn't really know how). Eventually, after some stupid discussion (I think he'd said climate change as fake or something like that), he sent me walls of text messages accusing me of manipulating him, trying to make him look bad (don't know to who), being brainwashed etc. I tried to push back, and to kind of explain how much that shit hurt (we'd been close for like 5 years at that point), but he just escalated and escalated. Eventually he was basically talking to himself, projecting like crazy, like "I know I'm not crazy" (I never said he was) and "if anyone needs a psychologist, it's you" (I never said he did). It got heated enough and he got hostile enough that I just had to completely disengage. That triggered him even more and he spammed me through every venue, in the end even with weird veiled threats ("watch what you get in the mail, bitch ;)) kind of things. I blocked him and went no contact.
In the years following I learned through mutual associates that he wasn't doing well, but most people sort of also stopped talking to him, so details were sparse. I felt like shit, like I abandoned a friend in a really dark place, but I had no idea how to help or even really make sense of what had happened. I had introduced him to a friend, who didn't stay in contact after the break, but had his facebook still. He told me at one point that he was posting completely unhinged shit. Literally that he had been kidnapped by the government and forced to eat clones of himself, and posting audio files of him talking to local police trying to report this kidnapping. I never listened, but my friend heard a few minutes and it was as horrifying as it sounds. At this point I figured it must be schizophrenia/psychosis, but I didn't even know where he was living (he was calling the police in a different city in the recordings), didn't know any of his family (and back when we were close I got the impression he'd broken with most of his close relatives).
He just contacted me today with the message "Hey, about back then - I found out that we only fought because some psychos were injecting us with serums that made us hostile to each other. I want to apologize, I was being crowd controlled for the last 10 years. I was being majorly timeline morphed, it was illusion of autonomy". I'm translating, but that was it, like almost word for word. Now I'm sitting here, all the old feelings welling back up, feeling so fucking sorry for my friend, but still just as powerless. He's clearly still delusional, but he feels some way about what happened, he is reaching out. What the fuck do I do? Do I respond? I want to tell him not to feel bad about what happened back then, like who gives a fuck, but I don't see a way to do that without implicitly agreeing to his delusional premise. I'm privileged to never have had to deal with this stuff, but I'm so lost. I have no idea if it would be harmless to hit him back or if it's like a massive bad idea.
Any input is massively appreciated.
TL;DR: Old friend who had a psychotic break and whom I lost contact with reached out to me, clearly still suffering from major paranoid delusions (he says he acted out in the past because of mind control drugs essentially), don't know what to do.
