Hammer it's been mentioned above that 'fleeing the police' is an allegation, that De Menezes 'vaulted ticket barriers' etc .. it's unconfirmed and those sources that say he did so ie newspapers are unreliable. If he did he only responded in the same way that anyone else would have done whether they were carrying shopping or a backpack full of explosives ... given the choice of 'fight or flight' if the odds are stacked against us we tend to flee.
As for the lack of attention given to the girl who was murdered in Brazil it was useful as a story for a few days merely to reinforce stereotypes of the feckless and reckless working class. Once they did that they moved-on.