This question already has an answer here:
As a normal, unprivileged user, I wonder what I should do if I encounter a post on any SE site which contains signs of severe mental health problems like paranoia or persecution mania, but not necessarily any suicide notes.
Last time when I stumbled over such a post, I left a custom moderator flag explaining that I think the user has mental problems. It was marked helpful later and the post got deleted.
However, I would like to ask whether that was the right way to react or whether I could/should have done something else. I didn't really dare to leave a comment regarding their mental state, as I feared it might worsen the situation. What about technical comments, e.g. if I can explain that something they see as threat is actually normal and why - should I post that? Or just flag it and leave?