It looks like the shooter in this particular case was adopted, recently lost both his foster parents to illness, and suffered from mental illness. I can't imagine what would be going through the mind of someone firing high caliber ammunition at unarmed children.
Some politicians will make the argument that laws cannot prevent the mentally ill from killing people, but I doubt there would be 17 fatalities if this is was the most dangerous weapon he had access to:
Totally in agreement with you, I believe that the politicians have a little reason in it but equally they must be more to the slope because this type of attacks and massacres are seen very often there