It seems obvious that firearms deaths are a multi-cause issue. If you have a highly developed country (Finland, Iceland, Switzerland...) you can also have lots of firearms without fearing also massive killings. But if half your society is born and raised under violence (El Salvador, Venezuela, Honduras...) + easy firearms + raging black markets operating freely, it's a recipe for disaster. I wouldn't expect less deaths in Brazil by getting more guns in the streets and encouraging resistance: Venezuela is already there (more than twice the guns of Brazil, handguns and semiautomatic are more or less allowed, you only need a license), and their death rates are the worst in the world.