The pistols, and yes I know, nothing has been proven.
I find it interesting that the youth would have been able to conceal a rifle while gaining access to the school. Not impossible, but much easier to conceal a couple of semi auto pistols.
Why conceal it??? He parked his car within 10 feet of the door and was in the school in a matter of seconds. He could have had a howitzer in full view and no one could have stopped him in that short of period of time.