The biggest factors do revolve around guns though. Not just numbers, but the culture which feeds into itself and the perception that guns are not a problem, but a solution ("The only way to stop a bad guy with a gun is a good guy with a gun"). Of course, this then provokes a "Have-a-go-Harry" take on confrontation where people who are woefully ill-equipped to deal with a situation attempt to do so. The lack of training, the fetishisation of guns, and the sheer number of guns are all extremely significant factors in gun crime. Take away any one of these and the rate of gun crime would drop significantly. Unfortunately, any solution has to work within the framework of "no further regulation" to even get close to implementation which rules out swathes of methods
I was reading a reddit discussion some time ago, where most commenters concluded that it's fine to shoot a burglar entering your house at night, which feels very alien to me. Sure, it's a frightening situation, but in my mind a burglary clearly doesn't justify the, potentially deadly, use of a gun. Those are not equal actions and measures.
Name one more western first world country besides the US, where cops shooting someone is hardly news. And no, the problem probably isn't guns.
In the US there's about 1 gun per resident, Germany 0.3, UK 0.06, and Canada 0.3. Meanwhile there were about 987 fatal shootings by cops in the US in 2016, compared to 13 in Germany, 4 in the UK, and 9 in Canada. Even adjusting these numbers for population and number of guns per resident, you will still be off by an order of magnitude.