No. We cant ban guns. Its impractical. There are too many, too easy to hide. The cops wouldnt follow that order, neither would the military.
Now...I do wonder what the Founders would have written if they had an epedimic of colonial schoolhouses being massacred with muskets and bayonets by fellow citizens. But they didn't, their society didnt do that, except through warfare when the Brits did it.
Mental health is an answer to start with.
Second, not a gun ban, but measures for gun security. This kid should never have been near guns. They werent his. He wasn't 21, so he couldnt leagally own a pistol anyway. And that rifle should've been in a safe, somewhere he couldnt get it.