Over on PJ Media they are saying that he was at school but in a totally different building and hiding in a closet.
He did rush home and get his recorder etc. - probably thought he would be able to get the story out before anyone else.
Yep, that's how it went down. People at the school were dead, injured, scared, afraid for friends, relatives, staff, and all he could think of doing was getting a camera to be a voyeur to their agony. That's just twisted. In the midst of suffering and terror the wheels in his head were busy turning on how to exploit it for himself. Scary dude.