Most of the recent mass shootings occurred in "Gun Free" zones- places where a person is not allowed to legally carry a firearm. This meant that there was no defense available for the victims, because only the shooter had a gun. Such places are a magnet for criminals. They don't obey the laws.
To reduce this kind of violence we do not need more strict gun laws. In the early 60's, there was almost no gun control at all, yet we didn't have mass shootings then. So the problem is not the availability of guns. The problem is largely a cultural one, which also needs to be addressed, but removing the right of self-defense only compounds it.
If an armed police officer is a deterrent to crime, then so too is a legal armed and trained citizen. Do not disarm us where we are needed the most