Was my brother delusional(need advice)?

Hi guys. How are you all? I live in Glasgow. I have a brother who is 23 years old.He is currently on antipsychotics for his auditory hallucinations.However he came up to visit me yesterday and he was behaving very erratically.I would say he was delusional. He was saying that the FBI were trying to kill him and that they were controlling his thoughts and actions.He completely believed what he was saying.Also he wouldn't eat any of our food as he believed we were trying to poison him!. I am really worried about him. He has a psychiatric nurse. Should i phone her today and tell her what happened?Or should i say nothing? I don't want him to be sectioned or anything.Thanks for your advice in advance.Take care.