Every time there's a shooting, liberals run around saying this proves we need more gun laws. I ask liberals over and over how exactly you are going to keep guns out of the hands of criminals every time you say you want more gun laws.
In particular, address given that drugs are illegal, and yet any parent knows any kid can get as much pot as they want. There are millions of guns in the US, millions more in the world. So don't just say more laws, explain how more laws are going to actually work.
So, there have been 7 shootings killing at least 10 people in the last decade. The only thing you've achieved so far is that no one was shooting back.
The Copenhagen shooting, the guy got off an estimated 200 rounds before presumedly running out of ammo and fleeing. That's what'll happen in every society that bans firearms. Only bad guys will have them, and they'll use them unchallenged.
So if we have gun laws, both criminals and non-criminals will have guns.
If we don't have gun laws, only criminals will have guns.

What?
You're going to have to walk me through that logic, sparky.
What good are gun laws if by definition, someone using a firearm criminally doesn't not do their crime because of the law, or some posted "gun free zone" sign?
Laws only effect law-abidding people, not criminals. And in a country like the US where there's about as many guns in private hands as there are people, legislating the problem away is impossible because even a full ban on new sales still leaves over 300 million in distribution. Countries with long standing bans like in Europe fair better only because it's had so much time to do its thing there aren't many guns in circulation anyway. But it's an unfair comparison to try and claim gun laws work because they work in countries where guns have been illegal for generations. Of course they work there, there aren't that many to begin with. The laws there then are redundant.