But I was peeved to see Dave Weigel and a couple others imply that having armed police presence at schools wouldn’t help prevent mass shootings there because, after all, Columbine High School had a sheriff’s deputy on scene when the shooting broke out.
That’s right, but it isn’t like the deputy was sitting around eating doughnuts during the Columbine massacre. He traded fire (that is, he drew fire) with Harris for an extended period of time, during which Harris’s gun jammed. The deputy and the backup he immediately called for exchanged fire with the shooters a second time and helped begin the evacuation of students, all before the SWAT teams and the rest of the cavalry arrived, and before Harris and Klebold killed themselves in the library. Harris and Klebold had an assault plan — a sloppy plan, but a plan nonetheless. They had dozens of IEDs, some of which detonated, others of which did not. And there were two of them. In this highly chaotic tactical environment, the deputy acted both bravely and prudently, and who knows how many lives he saved by engaging Harris.
At Newtown, Lanza was delayed from entering the school’s main entrance, and had to shoot his way in through a security window. His tactics were far less sophisticated than Harris’ and Klebold’s. It’s not implausible to think, afforded the time to respond by Lanza’s delay at the front door, an armed officer could have put him down before he began killing in earnest. Not a guarantee, but far from implausible.