everyone is always looking for a 'scientific' answer, but this is odd. Your child may be more sensitive to paranormal activity. Talk w/ your Preist & make sure to give your child(ren) a strong religious upbringing. I'd still seek the medical route, but before comatosing your child w/ meds, seek ALL routes. Take care!
Yeah, it's kind of irresponsible on your part to have just assumed he was doing it for attention before. No one wants to believe that their child has mental problems, but when it does happen they should be treated so they can be functional and have a fulfilling life.
I would post this in the Child Behavior Ask an Expert forum for professional advice.
Hearing voices is a 13 year old is something to be evaluated by a professional. You should seek a psychiatric evaluation so that a professional can advise you.