Gotta look at it as a per capita per population percentage to have the statistical significance align.
There are 686,665 police officers in the US (federal, local, sheriffs, etc).
1004 murders out of 686664 is 146 per 100,000.
The civilian stats we've been talking are violent crime though, not murder.
The US homicide rate per 100,000 is 4.96 in the civilian population.
Cops kill people 36x as often as civilians.
edit: bad data.... my rate of 16.3 per capita was for ALL OF THE AMERICAS, including the entirety of south america, which is the highesti nthe world. The actual rate for the US alone is 4.96 per 100,000.
For this to be complete we'd need the number of those that were unjust.
Homicide is a cause of death. Whether it's murder depends on the events and actions leading up to the homicide.
That probably vary depending on who you ask but all homicides or killings are not murder.