Active shooter protocol since Columbine has been first on, first in, search and destroy. There is no other acceptable response.
The cops not acting should be fired, decertified and thrown to the wolves for any applicable criminal and civil proceedings.
This^^^ 2 real cops and a Haligan tool would have stopped the shooter before the arrival of any command element. SOP in many jurisdictions. If you accept the badge you accept the risk that goes w/ it. It is indefensible to wait no matter the risk to the officers responding. Until a hot muzzle has been pressed to the perps eyeball it is a hostage rescue situation and no delay is excusable.
mike r