There will always be those in any population who have a propensity toward violent anti-social behavior. We might have been reading headlines about two to five people killed, and two or three wounded, if there had been one person present with a legal concealed- carry weapon to stand up and take the offender out.
The option for self- or group-defense should not be left to the anti-gun groups. When it is you, or a member of your family, looking in the barrel of a gun in the hands of a crazed killer or a gang member, your perspective will change.
The law won't stop the bullet, but a legal concealed-carry weapon in the hands of a trained individual definitely could have rewritten the history of this sad day.