Contrary to what you still claim, the man did not wear a "suspiciously heavy coat" but a light denim jacket (see also picture in this BBC article).
Despero and myself have already analyzed several additional aspects of this police blunder and have already answered the issues you continue to raise. Unless you have something genuinely new to add, let's stop dealing with this. It's an overkill!
Seems like you and Despero have a fairly high regard for yourselves, as though you're the final say in the 'facts' of this case. Actually, nobody knows all the facts yet, only what is being reported and assumed.
Funny thing here is though, the British police are rarely involved in shooting people at all, especially innocent ones. This occurance in London was certainly far more rare than shootings of innocent people in our own country. Consequently, I must trust that the London police didn't just collectively decide to choose a random victom and then go blow his head off. The link you provided to "prove" your assertions tended to make you appear wrong, very wrong. Every single story written about this event says the police were running after the suspect as he ran into the train. Unless the guy had the power of bi-location, (two places at once), I am going to continue to assume that the police RAN AFTER HIM because he was trying to elude them.
Lastly, I would like to say that as of this time it is believed that Mendez was innocent of being a terrorist. Apart from that, we don't know that he was 'innocent' of anything else. The facts will eventually all come out and be judged as they should be, by British authorities. (For the record, GB is a liberal, anti-gun nation. Most of their police still don't carry guns).
At some point in time Mendez was marked as a dead man, beleived to be a terrorist carrying a bomb. The police did what they were told to do. Somebody up higher made a horrible blunder, but under the dire circumstances that Londoners were living under something like this was just bound to happen. They keep slaughtering innocent Brits and everybody gets jumpy, anxious, trigger happy. It's just human nature.
I STILL BLAME THE TERRORISTS. No terrorism, Mendez is alive today.