The idea that gun control will prevent such things is a myth.
No kidding. No one is stating that gun control will put a complete halt to such acts of violence. Doesn't it strike you as odd though that we have some of the most liberal gun laws and highest gun violence in the developed world?
If his gun had been more easily/quickly accessible, he might have saved more people than he did.
"If ifs and buts were candy and nuts we all would have a merry christmas"
You do realize there is also the chance he would have gotten himself killed. Or killed someone else. Or have zero impact on anything at all. Working in the land of hypothetical is fun and all but is practically useless outside of abstract ideas.