Wonderful thing, 20/20 hindsight.Kroegen said:
Armed police, unfortunately, often (if not usually) aren't in the luxurious position of having such categoric data, and they have to act in accordance with their training, procedure, operational commands, relevant laws and the circumstances of the situation as they see it. They are, after all, Johnny-on-the-spot, and the ones who's butts (and lives) are on the line if they get it wrong.
This, unfortunately, will sometimes lead to innocent people getting killed and, tragically, that's what happened here .... as far as we know from the rather vague and confusing information that has so far been made public.
But you have to realise that when police are in this type of situation, they are aware that there will be a set of consequences if they fire, but a good probability of another set of consequences if they don't. And in this case, what they believed those consequences were likely to be was an explosion that would not only kill the "bomber", but the officers and probably dozens of innocent commuters. So these officers (it seems) acted under the belief that had they not done so, dozens of innocent people could have been killed.
Unfortunately, the world isn't as simple as the "100% sure" you'd require implies. It just isn't like that. And police have to deal with the world as it is and the situation as they find it, not as how they'd like it to be.
J-C de Menezes was unlucky enough to have a very nasty set of circumstances conspire against him and, it seems, a sequence of mistakes occur (though we'll know more when the report is finally published) and he paid for it with his life. This wasn't the first time, and it no doubt won't be the last time. But if you wait for 100% certainty, nothing will ever get done and sooner or later, they'll be a far worse and eminently preventable tragedy.
