I notice they were careful not to point out that it will take 5-20 minutes for police to arrive outside the site and maybe an hour or more after before your area is secured and you will be out of danger.
In the meantime, active shooters are now learning to look under desks for victims.
BTW, what type of firearm were those police using to protect themselves as they entered the building?
Using a gun in an active-shooter scenario is just crazy. The shooter might take the gun away from the teacher/staff/resource officer; a child could gain access to the gun and shoot up the school; the teacher/staff/resource officer might decide to shoot the kids in a fit of gun-induced psychosis.
Using a pair of scissors is eminently sensible: no kids have ever been hurt with scissors; a chid gaining access to scissors is OK because they would never use them to hurt another child; and as soon as a shooter saw the scissors, they would stop their rampage immediately because (as DHS tells us) scissors beats gun.