[IIAOPSW]

A) what was he on and B) are you sure it is just the drugs at fault here.

First, this sounds more like a DMT experience than anything. Loads of people convinced the "entities" are real. For LSD, this would be highly unusual.

Second, the one long term effect psychedelics arguably have any link to is triggering the first break in schizophrenics. Keep in mind it does not appear to cause schizophrenia, just trigger it if it hasn't happened already. So there's really really good reason to see if perhaps it wasn't just the trips leading him to this state.