Weapons have a multifaceted character. Weapons can, for example, be considered as a method or as an objective itself. It could be cool to hold a weapon, this is as an objective, because it is a passion. As a mean, you can hold a weapon for killing or to defend yourself against others.
As statistics we can see
1984 to 1994: 19 incidents
1994 to 2004 (ban is in effect): 12 incidents
2004 to 2014: 34 incidents
These statistics show the following idea that as an pragmatic effect, indeed, mass shooting has been reduced. I consider the law of arms to be influenced by the tradition of the place where the law is implemented. The number of weapons-related crimes is 25 times higher in the US than in any other developed country.