Upon closer inspection it seems it's more a result of decreasing accident rates than increasing homicide rates although that is a factor lately.

https://usafacts.org/articles/how-many-police-officers-die-i...

That gives a homicide rate for cops of about 7.5 per 100,000. That's a bit less than twice the US national average, and about on par with the overall murder rate in the Carolinas or Mississippi. Seems pretty good for a profession that would logically bring a substantially increased exposure to murderers.