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 woman lies injured after an incident on Westminster Bridge in London on Wednesday, March 22, 2017. A police officer has been stabbed near to the British Parliament and the alleged assailant shot by armed police. Scotland Yard report they have been called to an incident on Westminster Bridge where several people have been injured by a car. (Photo by Toby Melville/Reuters)

Female members of the PDI (Investigations Police of Chile) march during the traditional military parade as part of the independence day celebrations on September 19, 2021 in Santiago, Chile. This year the militar parade was celebrated with 30% of the staff present in pre-pandemic years. About 6,500 members of the Army, Navy, Air Force, Carabineros and PDI paraded. (Photo by Matias Basualdo/ZUMA Press Wire/Rex Features/Shutterstock)

In this photo taken on Friday, July 14, 2017, a student at a paramilitary camp for children calls the rank to attention outside Kiev, Ukraine. As the deadly conflict in eastern Ukraine entered its third year, some parents in Ukraine are anxious to make sure their children are ready to fight it, instead of swimming and playing volleyball. (Photo by Efrem Lukatsky/AP Photo)

Topless protesters from the organization PETA (People for the Ethical Treatment of Animals) stand with “banderillas” filled with red powder as about 100 people rally in front of the town hall square in Pamplona, Navarra, northern Spain, demonstrating against the treatment of fighting bulls in the Fiesta de San Fermin, 05 July 2017. The renowned eight-day festival made famous by Ernest Hemingway's 1926 novel “The Sun Also Rises” has running-with-the-bulls and a bullfight each day for the fair, which begins at noon on 06 July 2017. (Photo by Jim Hollander/EPA)

Graduates dance as they take part in a “Last school bell” ceremony at a school in Minsk, Belarus on May 30, 2018. (Photo by Vasily Fedosenko/Reuters)

Visitors wear shirts with an image of former Chinese leader Mao Zedong at the Shanghai World Expo site in Shanghai, May 2, 2010. (Photo by Aly Song/Reuters)

A stray dog is pictured besides a graffiti made on a shutter of a closed shop at a market area during an ongoing state-wide weekend curfew imposed by the directive of the Delhi government to curb the spread of the Covid-19 coronavirus in New Delhi on January 9, 2022. (Photo by Sajjad Hussain/AFP Photo)