Murder is a byproduct of crime. Crime is, largely, downstream of economic conditions with some obvious caveats.
New Hampshire has the 2nd lowest crime rate of the USA states. You could make the same argument for, say, Switzerland (high gun ownership but no crime/murder). But no one would be surprised if you had high gun ownership in Monaco.
Similarly for the ethnic argument you're trying to make: Majority black neighbourhoods in the USA tend to be poor. They also tend to be near more affluent places. Unlike poor white neighbourhoods, which are on average more rural in the USA.
Being poor, and being next to rich people, and being excluded from legal increases of becoming rich, will increase crime.
This should be obvious. Brazil has famously Favelas right next to wealthy areas and has a persistent crime problem for example.
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In short, it's really incredible how far some Americans will go to deny the obvious truth: *gun prevalence increases deadly crime*.
Sure, some cultural factors will increase crime/violence on the margin. But the reason y'all have a bunch of shootings is that you have a bunch of guns to do shootings with. That simple.