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It would be very difficult to determine what is the actual cause of these symptoms online. However, the symptoms you describe can be attributed to psychosis with the auditory hallucinations and paranoia. He is at the appropriate age for an onset of this disorder.
But, some chemicals and drugs also can create these symptoms. If you take him in to mental health, they can prescribe medications to assist with the symptoms, regardless of the cause. If he is using some sort of chemical, I hope he will become rational enough with medications to understand the effects the chemicals are having on him, and be more willing to stop chemical use.
Hope this helps. Gina