Government can not kill indiscriminately and as a show of force its own citizens as that would upset a lot of citizens as the government is meant to protect the

Government can not kill indiscriminately and as a show of force its own citizens as that would upset a lot of citizens as the government is meant to protect them from violence. It has the potential to stir up civil war. It is only then, in case of civil war, that governments chose to display their power in that open way. Its not the masses that are meant to be kept inline by this murder of a MI6 agent, its the people close to the victim - his colleagues and sympathizers.