Let's just make all guns (excluding certain guns ex. grenade launcher, bazooka) completely legal and all, make them easy to get, but with a lot of oversight.
Most of the people who go on shooting sprees don't apply for a gun permit anyway. They 'borrow' a gun from someone, because it takes to long to go and apply for a gun.
But if you make it easier for the psychopaths to get a gun, you can check their records and all when they are trying to get a gun, and maybe catch a shooting spree before it happens.