This country actually has a long history of gun violence in schools. I ran across an article that gave the first incident as being in 1557. The absolute worst was the "Bath Massacre" of 1927. Forty-eight elementary school students were killed, and another fifty-eight children and adults were maimed. The loon that did that used fire, and a bomb. No guns were used.
There are 20,000 laws in this country that restrict where law abiding citizens can carry a firearm. Never once, has a criminal or insane person honored any one of them. You can't legislate morality.
If ANYBODY can craft a law that will prevent evil people from doing evil things, I'd gladly grind all of my guns into very fine dust. Laws only take away unalienable rights.