who are only trying to stop us all from being killed / bombed/ blown up

The police acted the way they did because they thought the public were in danger. Mr. de Menezes acted the way he did because he did have things (small things - not terrorism!) to hide and wouldn't for one moment have thought the police would be thinking he had done anything seriously wrong. He wouldn't have realised that he was in danger. The whole thing has been a terrible tragedy, but following the suicide bombs in London it is not surprising that something like this has happened.

The people who should be blamed for this tragedy are the terrorists -they may not be directly responsible for this death but they most certainly are indirectly responsible.