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
As far as i know, i have met only one person like this.
A guy i knew in “highschool” (kinda equilevant) killed his friend a few years later while both were drunk and had just come out of sauna. He thought that his girlfriend had cheated on him with the other guy and woops, axe to the back.