The propensity to unwarranted violence is independent of available tools. Violence prevention should focus on the motives for violence more than on the tools, for we have seen no method by which the evil can be reliably disarmed without affecting the good disproportionately.
Some violence is instrumental: drug cartels are the prime example. They use force to achieve certain results. Some violence is expressive: mass murderers usually do it for the emotional experience. Neither can be substantially reduced except through changing the culture of the individuals involved, changing the incentives, and occasionally defeating the remaining violent actors in battle.