I guess it´s more complex than that, though.
From what one can read, the killer was suffering from a form of autism - and he used the guns of his mother. He killed her first, then went to the class his mother was teaching.
Although all these "details" may be misleading or not even accurate, one can suspect that behind the tragedy is another tragedy.
This is not to say that the killer´s deeds can be justified in any way.
But unless we understand why people actually go crazy to kill the innocent, our society will never be able to solve this problem.
I find it extremely sad that those who oppose gun control always point to the second amendment in these cases. Or that they want to justify the ownership of guns with the argument that not owning guns would not stop such shootings.
Fact: if you don´t have access to a gun you won´t be able to shoot someone. Fact: If you want to go crazy, you can do it with other weapons, even simple knives. Fact: someone running around with knives will not be able to kill so many people.