Not just uncaught murderers, there are a lot of people who have killed without legally being considered murderers.
People who killed people in accidents such as driving accidents or hunting accidents
People who killed in self defense
Soldiers who killed enemy soldiers
Executioners
Police officers who have killed on duty
Doctors and nurses who have made mistakes that accidentally killed patients
And the Untied States is the only country in the western world that still has executions
wrong, Europe still has executions because there are armed police killing drowning refugees in the Mediterranean or cops shooting Roma people