At the time the Columbine massacre happened police training was that the police should secure the area and wait for the SWAT team to arrive and possibly enter the building. Of course the shooters had long since run their course by the time SWAT entered the building. This was a wakeup call and police training changed in response.The training now has long been that the school should go into “lockdown”, people hide wherever they can, and they wait for the police to arrive. Upon the arrival of three or four police officers they would form a team and enter the building to engage the shooter. No active shooter incident has ever been stopped by such a multiple officer team.