Guns don't kill people, people kill people.
Why do people kill people? There are a list of reasons; revenge, anger, negative emotions and teachings... monetary gain, envy, insanity.
This all seems like a combination of mental problems that lead to murder. How would you solve this, if you ran a society?
Well, if murder was caused by mental problems, you would find a way to treat mental issues to stop it from ever happening. You would deny negative teachings from reaching the public, like the glorification of murdering your fellow man. Not things like killing for a cause, like a war, but issues like slaughtering innocence or those who oppose you for little reason. You would educate people, and teach them to resolve their confrontations through words, not violence.
If you want to test this, gather three children for an experiment. Give two of them a slingshot, while the third remains empty handed. For the first child, tell him the rules and consequences of his new toy, and to take it seriously; it's a dangerous tool if misused, and can cause serious harm. For the second child, tell him to have fun. And for the third child, tell him that slingshots can make you harm someone, and refuse to give it to him.
Generally speaking, children don't follow rules too well and have a poor sense of right and wrong, but teaching the child will result in different outcomes.
The first child will probably cause little to no trouble with his slingshot. He will shoot at trees and cans, and have lots of fun doing his own thing.
The second child probably wouldn't respond too well, and end up breaking a window or damaging property; he may even hit someone with it.
The third child may get in a fight with the other children for the weapon out of anger, and use a stick to slap one for the slingshot if they can't share.
These haven't really been tested, but using what we already know about children, we can deduce that this is a highly probable outcome from our test.

Did you hear about that new Bar that opened up, "A Murder"? It's horrible, yet scum still go there on occasion. There's four ways you can take to get there, too. Gun Road, Assault Highway, Poison Avenue, and Other Lane. Gun Road and Assault Highway are the quickest routes, while the other two aren't so much.
Well, we don't want people going to "A Murder" anymore, it's a bad place and the food sucks. But it's impossible to stop them if the roads are open to it! How are we going to combat this?
Ah, I know. Let's close down one of the roads, that'll slow 'em down, right?
**** , the blockade we put on Gun Road is useless! Turns out that you can take Smuggler Lane and get to the other side of Gun Road, ******* hell. That didn't work at all! And Assault Highway is just impossible to close, just like Poison and Other. And now, the people who live on Gun Road can't stop all of the traffic going around, it's ruining the value of their houses and people are getting hurt by it, not to mention the traffic on Assault Highway is terrible now!
Well, we can take out the blockade, and put up a tool booth and stuff... maybe that'll slow it down-nope, not at all.
Huh... if this place is so terrible, why don't we write terrible reviews about it? If we convince people not to go to "A Murder", we wont have the issue of people giving them business.
Nah, **** you! That's stupid, and it's not as fast as our cheap solutions to make lives harder for those who want to go to "A Murder". Who cares if it ruins people who live along the way? **** Gun Road, the people there are just so smug, being able to properly defend themselves!