Most of the world doesn't live in a country with second amendment.
All the commenters responding to you are so clueless that they can’t see there are no better systems from a cost benefit analysis. Law enforcement is barred by the laws of man and physics from taking prior history into account when assessing risks and every repeated tip of violent crime without any evidence must necessarily be responded to as legitimate at a level requiring military style intervention on the basis of anonymous testimony. There are just no better approaches