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
Went to high school with one.
I went to high school with at least six. I say “at least” because those are just the four I know about. Two killed people with their car, three went into the military right after graduating and did combat tours. Talking with them afterwards, it was clear they had 100% seen combat and killed people. And the last just straight up shanked a dude at a local fast food place during a drug deal.