These mass shooting events are much more difficult to stop then the average mass shootings that happen on a daily basis. Mass shooting is generally considered when someone shoots 3 or more people in one instance. When you see the stat of there being a thousand mass shootings or whatever the number was this year you need to step back and think. These are typically gang fights where someone shoots up a party or in a fight or something. Throw away guns are the big problem. I support the second amendment.
One big issue is that the national gun registry is literally a file cabinet system somewhere in Virginia...file cabinets for 400 million guns....in this day and age. So whenever there is a shooting a cop has to call this registry and a person has to go through the file system to find the guy and that can take weeks unless it's a high priority and they can do it fairly quickly. This needs to change. Next I think you need to prove someone keeps their weapon once they buy it cause too often these guys are used in a crime and end up in the water. The gangs typically get a clean record person to buy the gun, it's used and discarded rinse and repeat. If you buy a gun and say don't have proof you have it 6 months later no more guns for you since you can't be responsible. This should be at least a start.