It was John Zawahri’s failure to pass a background check that prevented him from buying a firearm in California several years ago.
So the 23-year-old obtained an “unfinished receiver,” the metal piece that holds the critical mechanisms that allow guns to fire, and built an assault rifle himself. Last summer, he went on a rampage at a college in southern California, firing about 100 rounds and killing five people before the police fatally shot him.
Zawahri’s assault became one of the most notorious cases involving unfinished receivers, which are unregulated and have become readily available for purchase online and at some gun stores. Officials from the Bureau of Alcohol, Tobacco, Firearms and Explosives view the spread of the receivers as an effort to get around strict gun-control laws, particularly in California.