MIAMI — Almost two decades ago, when Dylan Klebold and Eric Harris went on a murderous rampage at a Colorado high school, the first officers on the scene did exactly as they were trained: They set up a perimeter to control the situation, while contacting SWAT officers. Many of the more than three dozen killed and injured that day were struck by bullets and shrapnel long before SWAT arrived. Columbine changed everything. Since then, law enforcement in proximity of any active shooting scene have been trained to immediately confront and try to eliminate the threat — whether they’re heavily outgunned or not. That’s not what happened at Marjory Stoneman Douglas High School when confessed shooter Nikolas Cruz entered the freshman building and killed 17 students and staffers in a six-minute-long spree.