A policemn's reality is built on shifting sand.
Humans have long practiced human sacrifice, only the motivations have changed. How many other species do this I don't know. Today the state provides a license to kill provisionally. Split second murder decisions do not even allow for the forebrain to have a conscious say. But a murder that takes over nine minutes in front of a nine year old is more than most civilized people can accept as justified. Such deliberate action with forethought is a definition of murder. *So is war* but the state can declare such murder to be legal.
Law has made allowances for self defense. Some of you have experienced having to choose to use lethal force in self defense or not. Lets hope you chose correctly.
The subject of murder defines a culture imo.
In the US for example, lynching is not a federal crime.
Murder is both a state and personal decision. I hope we choose wisely.