First of all Adam Lanza, the Sandy Hook shooter, stole the gun he used from his mother, and by the way, it was a pistol that was used in the shooting not a AR15.
Another fact, almost all school shootings are caused by kids on antidepressant medicine.
Another fact, most criminals acquire guns by stealing them or buying them off the street. They are certainly not going to go through a background check.
Fact, defensive use of guns are not usually reported, only gun crimes.
Fact, in Switzerland firearms are issued to all citizens, when they become legal age, and guess what, Switzerland has the lowest gun related crime in the world.
All citizens are trained on how to use a gun and the bad guys know it. Chicago, on the other hand, has the most gun restricting laws in the country, and also one of the highest gun homicides.
Fact, the Second Amendment was written to protect the First and the Fourth Amendment protects us from confiscation.
Fact, examples of countries that have confiscated guns Cuba, Iran, Iraq, North Korea, China, Russia, and Nazi Germany, all totalitarian regimes.