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)

Yeshiva School students briefly dance on Grant Street after the menorah lighting outside of the City-County Building for the fifth night of Hanukkah, Thursday, December 26, 2019, in downtown Pittsburgh. (Photo by Alexandra Wimley/Pittsburgh Post-Gazette via AP Photo)

This picture taken on May 23, 2017 shows visitors posing for photos along a path at an Indonesian hamlet dubbed “the rainbow village” in Semarang, central Java, that has become an internet sensation and attracting hordes of visitors. (Photo by Suryo Wibowo/AFP Photo)

Britain's Prime Minister Boris Johnson gestures during a visit to Darnford Farm in Banchory near Aberdeen in Scotland on September 6, 2019. Prime Minister Boris Johnson heads to Scotland on Friday in campaign mode despite failing to call an early election after MPs this week thwarted his hardline Brexit strategy. (Photo by Andrew Milligan/Pool via AFP Photo)

A woman attends an opposition demonstration against presidential election results at the Independence Square in Minsk, Belarus on August 22, 2020. (Photo by Vasily Fedosenko/Reuters)

Robert Burck, better known as the “Naked Cowboy”, falls in the snow during a nor'easter storm in Manhattan, New York City on December 17, 2020. (Photo by Carlo Allegri/Reuters)

A boy with his bike is seen as rainbow appears after a rainfall in Edremit district of Van province in Turkey on July 08, 2020. (Photo by Ozkan Bilgin/Anadolu Agency via Getty Images)

Giant panda Shuixiu's two babies are pictured at their room in Shenshuping base of China Conservation and Research Center for the Giant Panda on November 3, 2021 in Aba Tibetan and Qiang Autonomous Prefecture, Sichuan Province of China. (Photo by An Yuan/China News Service via Getty Images)