>Why is the Brazilian police officer wrong when he kills someone and why is any other officer in any other country right when he does the same?

Who said that? They are wrong in many cases, whether the country.

>Mistakes happen it's part of this duty of being the police.

Killing urban poor indiscriminately whenever crime is suspected (or even widely overusing open fire even when crime is actually committed), are not mistakes, are policies. Fascist policies.

Brazil is as bad as the Philippines in this regard (and US trigger-happy cops and SWATing overuse are bad too, yes).