Beanbag rounds and similar technologies are absolutely incompatible with civilian self-defense. When police officers employ them — if they’re being tactically smart — they use them in limited situations as a last resort in an attempt to avoid having to use deadly force, but almost always where the use of deadly force is proper and legally authorized. Typically one officer employs the less-lethal method while at least one other officer covers the bad guy with a firearm.
In any deadly force encounter, and surely in school shootings, the three main issues to consider are means, opportunity, and jeopardy. Does the bad guy have the means — a weapon or obvious potential physical ability — to cause serous bodily injury or death? Does he have the opportunity? Is he within the effective range of his weapon? Is he putting people in jeopardy? Is he demonstrating his intention to cause injury or death? If all of these factors are present, deadly force is not only allowed, but necessary to stop the attacker.
In the Newtown killings, the killer began by shooting his way into the school and immediately thereafter began killing innocents. There could be no doubt of his intent or of the immediate necessity to stop him.
Probably the best illustration of the relevant issues was a bizarre 1997 standoff between a katana (Japanese sword) -wielding man and the Seattle Police. (Video of the incident, and an account.) In that case, all of the elements for the use of deadly force were present. The man had the means to cause serious bodily injury or death and he had the opportunity to do it. He was standing on the street, threatening anyone within range. Removing a sword from its scabbard for any reason other than cleaning or training is more than sufficient demonstration of deadly intent. While the man obviously knew nothing of actual swordsmanship, he was still sufficiently dangerous. The only element of deadly force that was lacking was jeopardy. As long as the police could keep the man far enough away from them and others, jeopardy did not attach, and it was not — until that moment — absolutely necessary to shoot him.
Many officers were keeping the man continuously covered with their firearms, and all kept cars and other solid objects between him and them. Had the man actually charged officers, as soon as he was within roughly 30 feet he would have died in a hail of bullets. He was shot — from close range — with many beanbag rounds, and also by what appear to have been rubber bullets. While some of them obviously hurt him, none of them incapacitated him, and none of them caused him to drop his sword or otherwise surrender.
The man was even enveloped in a cloud of pepper spray, which had no effect. He was finally subdued, after about eleven hours, by being knocked to the ground with what was essentially a water cannon, followed by officers pinning him with an extension ladder and a pole. Low-tech means won the day. The beanbag rounds — many of them — were ineffective.
Schools are generally poorly designed to deter shooters, and equally poorly designed for defense. Their long, open hallways provide clear fields of movement and fire for killers, and little or no cover for defenders. Less than lethal methods such as tasers or beanbag rounds are seriously range-limited.