In Norway, its illegal to have guns...yet they had a worse mass killing/shooting because the person got a gun and ammunition and went to an island park and randomly shot people for hours. The police and security were unarmed(and also shot) he wasn't killed. Only later in Oslo he was found and arrested. So how did that work? 
In our country, thanks to the PC-Dems it is against the law to share mental health records with Police or FBI so...mentally ill people can ACTUALLY  pass the gun reg and check. Lets start there.