As any Samurai warrior can tell you, it is not the volume, nor the power. of the projectile it is the accuracy. Spraying a crowd of people with bullets, although potentially horrific, is not as effective as one projectile (arrow, bullet, or any other penetrating item) placed between the eyebrows. In a situation like Aurora, the shotgun was the most, potentially, harmful of the choices available.
When used in an assault, EVERYTHING is an "assault weapon," even a rubber band or tennis ball. We need to address the "assaulter" not their tools.
When we quit honoring them with all the attention, headlines and infamy they seem to get, we may remove most of their prime motivation for these particular acts of senseless violence.