…..a lot of separate mistakes occurred for this to happen despite protocols. In medicine, we look at adverse events with this perspective to affect improvements:
Killer gave lots of warning signs on line which were ignored
Killer able to buy a gun without restrictions or evaluation
Mother not providing oversight
Teacher propped locked school door open a minute before shooter used this opening to gain access
School security guard not present (unclear on details of this as of now)
Killer shuts door to lock himself in with kids.
Cops arrive but cowardly wait and vacillate.
Cops hold back parents willing to go in themselves to save children
Cops block rescue team from going in to save children
The thing was an horrible series of mistakes. In medicine, we have found that these types of events are not usually fixed with just one adjustment, but with many.