The police narrative since the shooting has included,
1) that a teacher propped the classroom door open,
2) that the murderer closed it, locking it, after entering the classroom,
3) that police had to have a janitor open the door for them (which has never made sense).
The new narrative is,
1) the teacher propped the door open,2) (s)he left the classroom briefly to go outside to investigate the vehicle crash and saw the murderer shooting,
3) (s)he reentered the classroom, kicking aside the rock used to prop the door open and it closed...
4) ...but it did not automatically lock as it should have.
5) the murderer entered the classroom through the closed but unlocked door, locked the door, and began murdering,
6) the police used the janitor's key.