How many of the mass murders were committed by the legal owners of the guns?

Just because a small number of users of antidepressants committed these murders doesn't mean all people on antidepressants will break down and do the same. You may be shocked to find out just how many police and military are on these drugs and functioning just fine. The problem with using these drugs as a guide for not owning a gun would be figuring out who would be capable and who would not.

It seems it would be much easier to harden the targets than to try and make laws which will never have an impact on criminals or the mentally unbalanced anyway. Make it harder for a person with a gun to get into these places and use armed guards in the schools, some schools already do like NYC.

Laws do nothing to stop criminals from doing anything they want, the laws only allow the prosecution of these people when they're caught. How many people use seat belts or obey the speed limits all the time? Do those laws make everyone obey?