"Unarmed police officers are trained to wait for backup these days when suspects may be armed with weapons or explosives."

That is the crux if it. A policeman in that situation, knowing that should have recognised a duty to set aside such training and attempted to stop Menezes entering the station. There is clearly something badly wrong with any training which stops people behaving intelligently andn appropriately.

As for the shooting itself, Menezes was under restraint at the time he was shot in the head seven times. He had made no threatening movements. The claim that he had disregarded a warnig and moved towards the officers in a way that appeared threatening were seen by the jury as lies, and it seems reasonable to accept their judgement on this matter.

And in any case the assumption that shooting someoen is a reliable way of prveenting them detonatinbg a bob is a sheer assumption - it could easily work the other way round.