I confess; I have been guilty of various actions that other people have been executed by police for having committed.
As I understand it (from a small island where guns are not routinely carried, even by the police) Americans are not 'executed' by the police.
They are killed, possibly legally (in self-defence, or defence of the public), or by murder. There is currently a trial taking place in the US courts the outcome of which should be a guide as to whether the rule of law is paramount.