These firearm tragedies have to stop. Firearm owners have to take some responsibility, by keeping their guns in a locked, secure, gun safe.
It seems that most of these shootings are done by persons who do not have permission to possess them. I am a gun owner, but I believe that anyone who owns a gun used in a mass killing, which was not locked in a safe, might be prosecuted to some extent. Firearms locked in a gun safe cannot kill.