DNS, it seems like you are using shootings that don't meet the normal standard for mass shootings.
Some of the examples you listed involved shooting of family members or persons known to the shooter.
Some involved a shooting subsequent to a verbal or physical altercation.
I thought the way the government and media defined "mass shootings" or "spree shootings" required 4 or more victims; victims not friends or family of the shooter; not the result of another crime (such as killing hostages during a standoff with SWAT).
Using those criteria, the vast majority occur in either Federal Gun Free Zones, posted no gun zones, or in the case of Luby's in an area where there was no mechanism for lawful concealed carry.