So, the truth is we can't get people to turn in their guns and the freakout here in the US over that would probably itself be deadly. 

The truth is gun owners love their guns more than they love other people, including children. 

Two things happen whenever there is a big mass shooting here, gun and ammo sales skyrocket and gun owners squeeze their guns even tighter. 

So, we have to let them keep their guns and the truth is plenty of them are responsible owners BUT we should make them have to pay to keep their guns, per gun. This would likely reduce the number of guns out there and would as a bonus make it easier and add more things to the list you can charge a person who owns or uses a gun illegally with. 

There is no perfect solution for this, but much stricter standards for gun ownership, including having to have a yearly mental health check would be a step in the right direction. Good gun owners should have no issue with stricter standards.