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An evidence photo showing a bag and cartridge magazines is among several new evidence photos of the June 9 shooting rampage by John Zawahri that were released by the Santa Monica, Calif., Police Department at a news conference, Thursday, June 13, 2013. (AP Photo/Santa Monica Police)

From what I've been reading, the Santa Monica killer was packing an illegal assault rifle and 40 high-capacity ammunition magazines. He sprayed 100 bullets and had access to 1,300.

And, oh yes, he was a mental case.

The guy's exact background and how he obtained his war-ready arsenal weren't clear as of this writing.

But, regardless, there are at least two possible and troubling scenarios.

John Zawahri may have been an "innocent law-abiding citizen" until he wasn't -- until he murdered his dad and brother, then three others randomly during a 10-minute rampage.

If so -- if he had been a law-abider until he was suddenly a killer -- that would be yet another example of why we need to restrict the flow of the deadliest firearms into citizens' hands.

The 23-year-old also may have been psychotic. "He experienced mental health challenges," said Santa Monica police Chief Jacqueline Seabrooks.

If he were crazy or a criminal, it's all the more reason why we need to require background checks before people are allowed to arm themselves.

California imposes background checks on gun purchasers, but not on bullet buyers.

Felons are prohibited from legally owning or possessing firearms. So are people convicted of a violent misdemeanor or subject to a restraining order. Ditto someone held 72 hours for mental health observation.

Zawahri tried to buy a gun in 2011 and was denied permission by the California Department of Justice, according to Seabrooks. It's not clear why.

He apparently circumvented California's ban on assault weapon purchases by acquiring parts and assembling his own. So that law needs to be tightened.

And his stockpile of 1,300 rounds of ammo is evidence that background checks are needed for bullet buyers.

Guns don't kill people. Bullets do.

"We regulate firearms," says Garen Wintemute, director of the UC Davis Violence Prevention Research Program. "Firearms are nothing more than bullet delivery devices. If we're going to regulate the delivery device, we should regulate the bullet that the device delivers."

Such a bill recently passed the state Senate and is pending in the Assembly.

The measure, SB53, by Sen. Kevin de Leon, D-Los Angeles, would require a background check and license to buy ammunition. There'd be a one-time charge, probably $50. The ammo license would be permanent and attached electronically to the driver's license. The driver's license would be swiped at the gun store to verify that the customer was legal.

There are still some details to be worked out -- like how to control Internet sales and allow out-of-state hunters to buy ammunition in California.

But right now, De Leon asserted during the Senate debate, "You can walk out of San Quentin Prison ... walk into a Big 5, any mom and pop, bait and tackle store, in fact you can back up a U-Haul truck, and you can load up all the ammunition you want. No questions asked."

It would be an illegal purchase -- felons can't legally possess ammo -- but "there's no way to tell whether a person is prohibited," says Emeryville Police Chief Ken James. He is an official of the California Police Chiefs Association, which strongly supports De Leon's bill.

The bill passed the Senate 23 to 15, with most of the opposition coming from Republicans who voiced their usual complaint: The background checks would only harass law-abiding citizens.

One rural Republican, Sen. Jim Nielsen of Gerber in the Sacramento Valley, asserted it was part of an effort "to disarm Californians and Americans."

A bunch of gun control bills passed that day and moved to the Assembly, some perhaps relevant to the Santa Monica shooting.

SB396 by Sen. Loni Hancock, D-Berkeley, would ban possession -- not just purchase -- of high-capacity magazines, those holding more than 10 rounds. Zawahri possessed 40 capable of holding 30 each.

"You've heard that a ban on high-capacity magazines won't stop killers from killing," Hancock told colleagues. "But it will stop them from killing so many."

Responded Republican Sen. Stephen Knight of Palmdale: "It's not the magazines. These people have problems. They're crazy. You can't stop crazy people from doing crazy things."

Maybe not. But you can stop them from being armed for bear -- or, more specifically, for the mass slaughter of truly innocent people.

SB374 by Senate leader Darrell Steinberg, D-Sacramento, would ban the sale of semiautomatic rifles that accept detachable magazines, a feature of assault weapons.

"The reason the assault weapons ban has not worked as well as it should," Steinberg said, "is because the gun manufacturers have found every single loophole possible" to get around it. Such as selling parts so killers like Zawahri can customize their own weapons.

Another reason is there's no nationwide ban. Californians can buy assault weapons from private sellers at gun shows in Reno and Las Vegas and tote them back across the border. They can also avoid criminal background checks that way.

Whether any of the gun control proposals could have spared lives in Santa Monica -- or Newtown or Aurora -- cannot be stated for certain. But that's no reason to meekly crawl into a ball and whine that gun deaths are inevitable.

"There's nothing that's an absolute solution," says Los Angeles Police Chief Charlie Beck. "But if you put enough controls in place, that makes it less and less likely there will be gun violence."

"I don't think anyone can argue," Beck adds, "that keeping ammunition out of the hands of people prohibited from having it is not a good thing."

It might slightly inconvenience gun owners. But their convenience is trumped by saving lives.

Contact George Skelton at george.skelton@latimes.com .