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