Not sure if this is the correct sub for this post so my apologizes if so.

My cousin is going through some sort of mental issue were he thinks his house is 'tapped' or 'wired' from  the family of a girl he loved. 

He liked a girl who does not like him back and after the rejection he got from her and her family he has not been normal. He thinks his house has cameras installed by her family and is not in his right mind. I tried going to his house today to speak to him but he kicked me out saying I am part of the "clique" who installed the cameras. I even saw him talking to the vacuum as if someone can hear him through it. He is always on his laptop and saying the words "justice will be served". I tried to peak at what he was doing on the laptop and seen a picture of the girl he liked and her family members. He was completely normal just 2 weeks ago..

So my question is  who can I call or what can I do in this situation? I'm worried he could be a threat to himself and to others. Thanks