The tragic shootings in Colorado and Wisconsin demonstrate some hard truths. Mass shootings can occur anywhere, anytime. The bad guy has the advantage of surprise. The police are not going to get there in time to save anyone. If you believe that bad things come in threes, you should be prepared for a third attack.
As the last two videos show, before Columbine, the police training was to secure the perimeter and wait for the SWAT team. Now the training is for the first responder to go in after the bad guy. Police get shot when they do that, which is what makes the actions of Oak Creek Police Lieutenant Brian Murphy, who was shot 8 or 9 times, heroic.