California , especially Sacramento , has been a hub of ghost gun production . The ATF speculated in 2014 that there are tens of thousands of ghost guns in California alone . Four noted crimes in California were committed with ghost guns : a murder-suicide involving college students in Walnut Creek , a shootout between hostage-taking bank robbers and Stockton police officers , a mass shooting at Santa Monica College in 2013 by a student who was prohibited from owning a gun , and a shooting spree at Rancho Tehama Reserve in 2017 by a man who was served a restraining order that barred him from possessing guns . Proponents of ghost guns include gun rights activists and anarchists . They say that making weapons is the right of every American which maintains the privacy of gun owners . Individuals have organized " build parties " where equipment and expertise are shared to help create ghost guns . Advocates say that ghost guns are used in crime rarely despite widespread ownership . Gun rights advocates and law enforcement say that , because of the cost and effort needed to create ghost guns , criminals are more likely to use commercial weapons instead
shooting spree at Rancho Tehama Reserve
Rancho Tehama Reserve shootings
Ghost gun