Parents discover human head in son's closet

I just watched the first 40 minutes of the video. How are these investigators so calm when he's detailing every single thing he does. I would be shitting bricks out

So calm yet so terrifying. No cuffs on him or nothing, it's like they don't view him as a damn threat. Kinda what his friend mom said how he was a bit of an oddball but never thought he was a danger...