We know it's him for the following reasons:
1)-He's bragged about doing it while on other sites and to people offline.
2)-He exposed himself about 4 years back when he got caught posting Child Porn.
Basically admitting it here on the board, while posting a picture of himself giving us the finger.
(If I attach it, my whole post will be deleted. Understandable.)
3)-I know his family. Same school here in Virginia Beach. he makes admissions and confirmation acknowledgements accidentally, when he gets called out and starts "Magoo-ing". (His nickname from school days.)
There's a huge history there, too much to really lay out completely.
Everyone's probably sick of hearing about it. He's been doing it for years.