Actually, our Police-Prison-Indsutrial Complex is pretty much a violation of the Third Amendment. The Founding Slave Rapists weren't complaining about troops in people's houses, they were complaining about large military concentrations in the cities. The Founders would be horrified to see that the interpretation of the Second and Third Amendments have led to the current state.
Also, since some of the shooters weren't minors, we can argue at least THEY were in compliance with the law until the shooting started.
This wasn't the FBI, it was the National Youth Gang Survey...
Only 13% of homicides are gang related.
only 2000 or so of the 43,000 gun deaths we have in this country every year... all of which could be prevented.