Post Columbine things changed.
One of the biggest questions that came up after Columbine is how come the police did not go after the shooter.
Police later caught hell, justifiably, for taking a non-confrontational approach while people were being shot and killed.
So to refut your statement, yes at least a trained police officer would have fired back. I know a dozen shooters I would trust to respond in such a situation.
If a person is already indiscriminately shooting dozens of people, a few stray rounds from someone firing back is of no concern.
Odds are pretty good the shooter will flee from a few very unexpected shots being fired back at them. The hesitation caused by a few rounds fired at him could have bought the seconds people needed to escape to safety.
Maybe a few people might have been hit in the cross fire, but I highly doubt the bottom line totals of killed and wounded would have been anything but lower if someone was firing back at him.
