This is not actually about gun law. This is about crime in general. I have read a DOJ report in 2017 for my final year Law School thesis, the DOJ report states majority of the gun dead IIRC it's around 60-70% is through gang related crime and majority of those crime happened in West and South Western United States.
Mass shooting without gang affiliation is actually not that many in term of %, I don't really remember the number on top of my head but it was quite small, like 1-2%. Another issue is weapon that obtain illegally, the same DOJ report suggested that 90% of gun used in crime are obtained illegally. Either were stolen or unregistered.
On the other hand, to deal with mass shooting is not something you can do with getting gun off the street, even if they are doable, because it is on the mind of preparator, if you are a criminal, then chances are you won't go thru licensing and get guns to commit your crime, you would steal it so it cannot trace it back to you, and if you are just a normal person gone mad and murder everyone, well, you would still have that thought even if you don't have access to gun. You would just go kill people by stabbing, or by ramming people with car.
I need to declare I am neither a gun right or gun control lobbyist, I don't use gun, I lived in Hong Kong which is illegal to own guns and I am currently studying in Australia, also illegal to own guns.
