This was from a CNN story at the time:
The rampage might have resulted in many more casualties had it not been for the quick response of a deputy sheriff who was working as a school resource officer at the school, Robinson said.
Lessons of Columbine and other school shootings helped in Arapahoe
Once he learned of the threat, he ran -- accompanied by an unarmed school security officer and two administrators -- from the cafeteria to the library, Robinson said. "It's a fairly long hallway, but the deputy sheriff got there very quickly."
The deputy was yelling for people to get down and identified himself as a county deputy sheriff, Robinson said. "We know for a fact that the shooter knew that the deputy was in the immediate area and, while the deputy was containing the shooter, the shooter took his own life."
He praised the deputy's response as "a critical element to the shooter's decision" to kill himself, and lauded his response to hearing gunshots. "He went to the thunder," he said. "He heard the noise of gunshot and, when many would run away from it, he ran toward it to make other people safe."
So, a good guy with a gun (and others) ran toward the shooter, and along the way warned people to take cover.
But I see no indication that he drew his gun, or that the shooter thought for sure someone was coming to shoot him. All we know is that he knew somebody was coming, and apparently he wasn't planning on a gunfight involving anyone else.
The resource officer on duty definitely was a hero, and did his job as someone in his position should. But implicit in the statement about "a good guy with a gun" is that the good guy is drawing it and shooting to kill.
If this proves anything, it's that having a trained professional at the ready -- not teachers or janitors or students carrying weapons -- can make a big difference in these situations.
