Hoping that you've already cleared out the problem. I think all the advice and discussion that preceded was surely very helpful, but wanted to add a cleansing I learned from a psychic in NM.
You mix ammonia with water (as directed on the bottle--something like 2 tbs to a quart or more, please check.) and pour it into a fine mist sprayer.
Open windows wide.
Go all around the house. I'd suggest starting with the room then moving out and up.
Light mist around all windows, corners, and doors. Open cabinets and spray in front of them (not inside, just to clear and draw out the energy). lightly spary the air moving to the center. In bedrooms, go around the be 3X then verryy light across pillows.
in a bowl mix salt with water. Go around again, this time flicking out droplets of water around the room while saying:
salt and water by casting thee, make this place both light and free, and all my power keep for me, and it IS my will, so WILL it be!
The woman who gave this to me, Jackie Littlejohn, explained that energy pockets collect in rooms where we sit and think or hover too much and over time create eddies that seem to pull in more negativity.
I recently did this again after a number of years and again my reaction was WOW I (and others have said it too) literally see the quality of the air liglhtening.
If metaphysics is uncomfortable, please checkout newer physics, like books written by Fred Wolfe, to help offer explanations for why this works.
I hope you had some feedback from the gaming group. Games do pull kids in so strongly, as do other things, so I hope you also were able to have a very good, open minded professional check your son and give positive advice on his hearing these things. Often it is a mix of the metaphysical and the personal psyche, so very good to cover all things.
He's lucky to have a parent who will work thorugh these things with him with an open mind to all the possibilities!!