In late July, police say 21-year-old Scott Bertics showed up at a house in Walnut Creek and shot and killed 19-year-old Clare Orton before using a second gun to kill himself. While both had been in a relationship, police are not saying what prompted the young man to commit this crime.
But police told ABC7 News that both handguns were homemade, built by the Bertics who ordered the parts through the mail.
"There is no indication that anybody had any knowledge of what he was doing," said Lt. Lanny Edward. "And nothing illegal from the retailers' stand up of selling these parts. They can do that."
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The firearm industry calls them "ghost guns," which means they're made using different parts, don't have serial numbers, and don't require background checks.
Senate President Pro Tem Kevin de Leon, D-Los Angeles, has tried unsuccessfully to pass legislation restricting them. Their parts are not hard to find including unfinished lower receivers.
"This can be purchased online, it can be purchased at gun stores, it can be purchased at county fairs when they have gun expositions," he said in a video posted by CASenDems.
The Bureau of Alcohol, Tobacco, Firearms and Explosives says they are legal to build in California.
"It's not unlawful for someone to manufacture a homemade gun unless they are a prohibited person and in violation of any state or local law," said ATF spokesperson Helen Dunkel.
Several websites are dedicated to selling the necessary parts to build any firearm.