a trained, armed, uniformed officer has failed to confront a shooter in a school. There has been at least one other case of this occurring in the US, as I heard on the news this morning.
I suspect that this is not unusual when the armed intruder has a clear and overwhelming advantage in firepowe, like an assault rifle and multiple high capacity magazines. There may very well have been some other very good reason for this, I don't want to judge someone when I don't know all the details. But the fact is that sometimes a good guy with a gun doesn't kill a bad guy with a gun, and sometimes he dies trying.

In the Gabby Giffords shooting incident there was an armed concealed- carry licensee on scene and he wisely chose not to draw his own weapon. He correctly reasoned that a gunfight in a panicky crowd might cause even more casualties, and he realized that if there was a third armed person present he himself might have become a target. Instead, he bravely tackled the shooter and helped others subdue him until police arrived.

Firearms do not solve security problems. They just change them, and not always for the better.

Besides, when someone decides to carry out a mass shooting, its not likely the mere threat of armed resistance is going to deter him, as our brave, warrior president seems to think. I have a feeling the mass shooter is already resigned to his own death by police bullet, he is expecting armed resistance and he is fully prepared for it.

As usual, the tough-guy NRA gun nut-type strategies to supposedly deter and neutralize muckers are just what you would expect from cowards and armchair Rambos who have never been in these situations and not fully thought them out. Even dedicated and trained professionals, such as police and soldiers, never know how they will react in a panic scenario. People hesitate, and they freeze, or they make mistakes. That same radio show I spoke of mentioned the case of an officer who was confronted by a murderous shooter during a routine stop. Rather than drawing his weapon, he ran away, tripping and stumbling onto the ground. When his training finally kicked in and he got up to confront the gunman, he did not realize his gun had fallen out of his holster when he fell and he found himself pointing the finger of an empty hand at his assailant. I wonder if he said; "bang, bang".

In highly stressful situations, people cannot be trusted to react appropriately. Thoughtful, smart people know this. Careful screening and intense training is useful, but it doesn't always work either. Only long experience can build up the confidence to go into combat with some degree of assurance you will emerge alive. As for myself, I do not know how I would react in a situation that desperate. I'm pretty sure I could shoot an intruder who broke into my home, but I'm not certain I wouldn't panic or freeze. No one knows until they've been there. I know myself well enough that I would never carry a weapon outside my home where I might be tempted to use it unnecessarily, or worse, bungle it when I did.

Gun nuts aren't too bright. They don't think these things through. They are arrogant, overconfident, and inexperienced; a bad combination for a man carrying a deadly weapon into an uncertain place.