The teenage gunman in the Nov. 14 shooting at Southern California’s Saugus High School used an unserialized “ghost gun” that was assembled from parts, Los Angeles County Sheriff Alex Villanueva told the local ABC News affiliate. Villanueva said investigators were still trying to determine how 16-year-old Nathaniel Berhow came to possess the weapon, and who built it and when. “The mystery is trying to piece together who assembled what and at what point in time,” Villanueva said. The sheriff also told ABC 7 that police had still not determined a motive for the shooting and that federal agencies were helping to unlock Berhow’s smartphone. He added that some 45 interviews, including with the gunman’s mother, did not shed significant light on why the teen attacked his Santa Clarita school that day. Berhow shot five classmates, killing a 14-year-old boy and 16-year-old girl. He then shot himself in the head, according to the school’s surveillance video, and died one day later in the hospital. Officials recovered six weapons registered to the shooter’s late father in the family home.
Without a serial number, these guns are easier to buy and untraceable to authorities because they are built under the radar. This allows for minors and those with criminal records to buy firearms without a background check and without a paperwork trail. According to the ATF, 30 percent of all recovered guns in California are unserialized.