So I was working with someone from a different University on a project and I have started to become very concerned about their mental and physical well-being.
The messages which they sent me a day before came across as paranoid, saying that he believed that one of his colleagues had hacked his laptop and was following all his activities, just for the purpose of knowing whether they had secretly been getting guidance from someone else to help him write his papers in order to bully him and harass him.
Today he stated that he was no longer able to continue working with me on the project because of this harassment from colleagues. Again, the messages were quite concerning: for example, talk of not having been able to sleep for 36 hours and fear of dying in 'terrible suffering', but furthermore that one of his colleagues is poisoning his food so that he is unable to sleep and that he is really scared of dying because of not being able to sleep.
My first thought was to write to his graduate school where he works as a postdoc and state that I am concerned about his mental health and make a suggestion that his workload be lightened and that he be given the opportunity to speak with a mental health professional. Also, that perhaps there could be some words had about the culture of 'banter' and 'jokes', since he obviously takes these jokes very badly although perhaps they are not intended to be harmful (to be clear, I am a student and have no power in enforcing this, it's just a suggestion I want to make).
However, I am not sure how best to phrase this email (or even exactly what I should say) without 'getting them into trouble' or making it look like 'I am telling on them' or giving away confidential information. Also, who should the email be sent to? Again, I don't want to make things worse, but I feel like this is genuinely concerning and that someone should say something to prevent the situation escalating.