"The gun used by the government-hater to kill a checkpoint screener and wound three others? It was the type of firearm that would have been banned from the California market under legislation vetoed by Gov. Jerry Brown. Not that it would have mattered for Gerardo Hernandez, 39, the TSA agent who was murdered. The bill would not have taken effect until Jan. 1. And Paul Anthony Ciancia, 23, the disgruntled, alleged assassin, could have kept his semiautomatic rifle by registering it. And, yes, he also could have armed himself with a handgun and probably inflicted the same damage. But presumably he chose the Smith & Wesson M&P 15, .223-caliber semiautomatic — hauling with him five loaded detachable magazines and a trove of ammunition — because he had in mind creating even more mayhem. Such military-style assault rifles, after all, are the weapons of choice for mass killers. Ciancia was stopped only when critically wounded by LAX police. SB 374, by Senate leader Darrell Steinberg (D-Sacramento), would have banned the sale of most semiautomatic rifles capable of accepting detachable magazines. The aim was to close a loophole used by gun manufacturers to circumvent California's ban on assault weapons. Because of Brown's veto, these especially lethal firearms are still available for purchase in California. And they'll continue to be used by wackos in horrific shootings."