The police in my area have conducted school shooter exercises using real schools the exercise in one case involved two people pretending to be shooters.
The ideas in the exercise.
Respond quickly, get out your tactical weapons and go in for starters.
Get your body armor on as well act as quick as you can and these officers did that as you see in the video.
Officers with tactical weapons street patrol officers with sidearms working together to take out the attacker.