There is nothing wrong with having many more people trained to help in an emergency.  It doesn't have to be a mass shooting - it can be an auto accident, a light rail accident, an explosion caused by a faulty water heater or underground gas/oil, a roof collapse in the mall, a car running into a store or restaurant, etc.  While everyone should ideally be trained as part of high school education, the fact is that not everyone pays attention when they are 15 or 16.