Let us be honest with one another - shooting and killing an "Active Shooter" is easy. It is solely a matter of overcoming the ingrained hesitation that has been trained into the modern American, and the existence of sufficient marksmanship skills. That is all. And what is happening will be quite clear to any intelligent first world people on scene. It will be clear because it has happened time and again. The paradigm has been established, we know what will happen and thus we are prepared to take action. Moreover, we can often wait until the terrorist has actually "opened the game" with the deployment of his rifle...maybe even his first few shots.
So in essence we are still reactive to him. But what would it take to justify in your mind, killing the active shooter before he takes his first shot...truly before he ever gets his rifle out? What sort of information would you need?
I expect that - today - if one of us saw an Adam Lanza type guy with a rifle walking toward a Pre-School...or a Farooq/Malik Team walking with rifles toward a business, we would quite legal in shooting and killing them from ambush on the spot. Whether our first impressions were correct or not, based on the reality of today and what we have seen in the past year, the justification is there. But only because it would be easy to point out to what Lanza-Farooq-Mateen, et al, have already done. Failing in that collective knowledge, maybe we would not.
So that brings us to the Suicide Bomber. Clearly allowing him to "deploy his weapon", or "fire a shot" is an untenable plan. With these types of attack, you are either preemptive or you are dead. Will anything I say here change people's minds on this by the mere reading of my words? No...not what I expect anyway. But it will begin the paradigm change...or at least the realization that it must in fact change.
What will change the paradigm from reactive to proactive? Multiple suicide bombers successfully carrying out their murders in the USA. the reason we are comfortable with proactively interdicting the active shooter is that his existence in our world is common. Not so with the bomber, but sadly, I think that will change. One does not "arrest" a suicide bomber. Nor does one "defend" from him. He is detected to the best of the ability of those on the ground, and when the weight of the presented information is sufficient, you interdict him.
And yes, this will involve directly interdicting (nice set of words that stand in for ambushing and killing) those who are suspected of wearing an IED. Disagree with me if you wish. Call me "insane" like those silly gun writers on the internet. But come and talk to me after a few of these go off in soft targets in the USA.
Now, please do not respond with fearful indignation. I am not suggesting you shoot someone wearing an overcoat in July. The overcoat is but one factor. If you see several of these indicators, and you are at a soft target, and the subject is mumbling prayers in a language you cannot understand, and the timing of things is good for a bomb...well, you will have a decision to make. Eventually, the death toll will make it as easy a decision as shooting the active shooter in the face.
TARGET INDICATORS - SUICIDE BOMBER
Clothing that is bulky or excessive for the weather (to hide the bomb)
Hands hidden (possibly holding the switch to detonate the bomb)
A strange chemical odor or excessive cologne to cover up that smell
The bomber focused, but unresponsive. Suicide bombers are usually unresponsive to questions or commands
Heavy luggage or backpacks that don’t fit the situation. The average weight of a bomb used by a suicide bomber is around 20 lbs. The Madrid train bombers all had very heavy backpacks. The Moscow bomber placed his bomb in a rolling suitcase. Not all the bombers wear their bombs.
Nervousness, excessive sweating, or repeated mumbling of a prayer or mantra
Exposed wires anywhere on a person’s body
Repeated attempts to avoid security checkpoints and/or police officers