The problem is bullying, not gun laws.
I come from New Zealand, and I live in the States now. In New Zealand we haven't had a school shooting since 1923. The gun laws are fairly similar except that there is nothing equivalent to the second amendment.
I have no objection to the second amendment, to me it just seems like a redundant clause, like the right to own a car or the right to own a knife. One already has the right to own property, which extends to movable objects as well as land. The right to 'bear arms' is vague. It is not limited to and not specific to firearms. Carrying a sword is bearing arms, or raising a chair over one's head in a position to hit someone with it is bearing arms, so restricting guns or even banning them entirely doesn't actually affect a person's right to bear arms.
When you say Ban, what people understand is 'blanket ban'. They tend to think you want to make guns illegal for everybody. You need to be more specific about what it is you're intending. I'm assuming you don't want it illegal for policemen or soldiers to carry weapons. You probably have no objection to recreational firearms used for hunting or other sports. You may or may not be okay with handguns for protection, and only wish to ban automatics and semi-automatics. I don't know, because you have not specified. I'm assuming you're a rational person and have thought your opinion through thoroughly, but most people won't give you that courtesy it seems.
History has shown us that heavy laws, like a blanket ban on alcohol, only makes criminals out of everyday people. If a blanket ban on guns were to be imposed it would have a similar affect. People would still be able to access guns, and even if they couldn't, other weapons might be obtained.
The questions we should be asking is NOT 'how did this person get a gun'
but:
"Why did this person get a gun?"
"What drove them to it?"
"What is wrong with our culture that makes this happen over and over again?"
Have you ever seen the movie Carrie?
The movie shows us that her powers were not what was wrong. People were afraid of her powers, but She could have used her powers for good. All the pressures in her life, an over-bearing parent, students bullying her, ambivalent teachers, it all just made her snap, and drove her to do destructive things.
Now ignore the fact that she has supernatural powers. What if she instead had a gun? Not much would change. She could probably still destroy half the students at the prom, instead of all of them. What if we gave her a sword? Now were, starting to talk, right? She couldn't kill the whole school with sword. Just a few students before the police got to her. But wait, let's make swords illegal now to. Now she has a knife, that's one student killed at best. Can we make knives illegal? Impossible, we need knives in our everyday lives. So we will have to settle for only one student gets killed. It's better than the whole school right? Of course it is, it's perfectly rational... or is it?
What if we changed something else? Carrie can keep her superpowers, her gun, her sword, and her knife. If wouldn't matter. Perhaps if we changed the story so that her mother wasn't bat-sh*t crazy, or if we gave her a few friends to stick up for her at school, or if her teachers actually gave a damn. Maybe then Carrie would have been somebody amazing. With her powers she could have been a superhero.
Banning guns won't help anything
Keeping guns won't help anything
If you want to help, you must change the culture. We should care about each other. Be the change you want to see in the world.