In the Santa Monica shooting, the criminal BUILT HIS OWN GUN. Assault weapons are banned in Cali and he was able to build his own. There's always a loophole for murder. Stop lying to yourself. You know they don't work very well. If a criminal is denied to buy a gun, he can just go to the black market.
People often compare us to Australia stating that after their gun ban there were no more mass shootings - but there was. It happened at Monash University. Because there were less than three people killed, they say it doesn't count. If anything, it's not a mass murder, but a lot more than three people were shot so... People have been killing people since the beginning of time. Removing the innocents' ability to defend themselves won't make it better.