Like you the vast majority of people, both in the UK and abroad would agree with you regarding the unfortunate death of the Brazilian man. A tragic mistake.
I'm not sure that the vast majority would agree with your latter statement, "I hope it makes it clear that the British people will not accept an ends justify the means let's shoot and ask questions later policy."
Hindsight is a wonderful tool for argument and as somebody pointed out earlier, if he had been a bomber as suspected, then the officers would be facing recommendations and medals.
I'm not sure where you arrive at a, "let's shoot and ask questions later", but you make it sound like a flippant policy on behalf of the police for some random individual John Wayne lookalikes.
Correct me if I am wrong and please allow for the pressure that the police were under at the time of the incident, but wasn't the man followed from a house under surveillance at the time, dressed in an abnormally warm/padded coat for the temperatures of the day, requested/commanded to stop by the police, then jumped a set of turnstiles to run away eventually ending up on a crowded train? This man had lived in the UK for 3 years and could speak excellent English.
Did anybody else in the vicinity make the same decision as him and run when the police arrived on the scene, or was he the only one?
Nobody wants a police state and nobody is going to get one, but you have to let the police get on and do their job with support from all. Under these present circumstances and under pressure that you have never encountered, unfortunately mistakes may be made. Nobody wants it, nobody chooses it, especially the police.
Own up anybody who has never made one.