By far the easiest way how to "operate" is to avoid bad neighborhoods and police them only very lightly, leaving a power vacuum for the local gangs to step in. Criminal-on-criminal kills do not elicit as much public response.
Of course, the result is what the French call "lost territories of the Republic".
The "criminal-on-criminal" crimes may not make the news, but they end up being used to push for stricter gun control laws.If I remember correctly, the majority of gun violence and mass shootings is done with hand guns, is gang related, and mostly contained to some very violent areas in cities. Politicians and the media try to make it seem like the shootings are all done by right-wing radicals killing kids with AR-15s.
Yeah, I surprise my fellow Europeans by explaining that homicides (by gun or other means) are extremely unevenly distributed in the U.S. and that, depending on where you live, your safety may be on the level of Reykjavík (basically a peace heaven) or Johannesburg (living hell), with local gun ownership rates having only a very loose correlation to crime, if any.
Statistics, of course, are often made to include all gun deaths, and it would also be interesting to see whether the overall rate of of suicide is affected by levels of gun ownership.
You shouldn't try grabbing a cop's gun in Germany, or come at them with a knife, because you might get shot. I don't think it's that different in countries with armed police.