An unknown number of guns are being built with the mechanisms, causing problems for the police and ATF officials. Photo: An ATF agent holds a generic unfinished receiver, back, and one that has been manufactured, front, at an ATF field office in Washington, on May 06, 2014. The ATF is trying to crack down on the trade in the makeshift guns by targeting shops and individuals who offer to turn the unfinished receivers into functional pieces for firearms. (Photo by Bill O'Leary/The Washington Post)

A radio-controlled flying witch makes a test flight past a moon setting into clouds along the pacific ocean in Carlsbad, California October 8, 2014. Reuters was invited to photograph the testing of the life sized device by inventor Otto Dieffenbach lll. (Photo by Mike Blake/Reuters)

A partially frozen Niagara Falls is seen on the American side lit by lights during sub freezing temperatures in Niagara Falls, Ontario March 3, 2014. (Photo by Mark Blinch/Reuters)

PETA (People for the Ethical Treatment of Animals) activists protest in front of the venue during the Berlin Fashion Week Autumn/Winter 2019/20 in Berlin, Germany, January 15, 2019. (Photo by Fabrizio Bensch/Reuters)

A woman yawns as she sits outside a hospital on a cold winter morning in Srinagar January 3, 2019. (Photo by Danish Ismail/Reuters)

A helicopter flies in front of the Wolf Moon as it rises over London, England on January 20, 2019. The Wolf Moon, the Full Moon on January 20-21, 2019, is a Supermoon, making it look bigger and brighter than usual during the total lunar eclipse. (Photo by Dinendra Haria/Rex Features/Shutterstock)

Noel Brandon known as DJ IAMNOEL plays his set on a balcony in downtown San Diego, California on April 11, 2020. NOEL was inspired by other countries and wanted to give back. Residents went on their balconies at 8pm to cheer in support for the frontline workers, afterwards NOEL played his set to cheer up the locals who have been quarantined like many other cities around the world due to Coronavirus. (Photo by Ariana Drehsler/AFP Photo)