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)

Aleksandra Krunic, of Serbia, drops to the court after defeating Petra Kvitova, of the Czech Republic, during the third round of the 2014 U.S. Open tennis tournament, Saturday, August 30, 2014, in New York. (Photo by Kathy Willens/AP Photo)

Brazilian Treatment – Mario Testino teams up with American beauty Karlie Kloss for a story lensed in Bahia, Brazil for the July issue of Vogue US. Stylist Phyllis Posnick selects a wardrobe of colorful looks for Karlie to wear as she heads to the beaches and other stunning sights of Bahia. Whether posing with Capoeira dancers or exploring the outdoors, Karlie enchants in every image. (Photo by Mario Testino)

An ultra-Orthodox Jewish man inspects an etrog, citrus fruit used in rituals during the upcoming Jewish holiday of Sukkot in Jerusalem's Mea Shearim neighbourhood, October 13, 2016. (Photo by Amir Cohen/Reuters)

The luxury Jetstar private jet, built in the seventies and retaining most of the original features which is now being used as a holiday let is seen in Redberth, Pembrokeshire, Wales, January 11, 2017. (Photo by Rebecca Naden/Reuters)

A girl peers from between light decorations at a Christmas fair which opened ahead of the holiday season in Bucharest, Romania, Friday, November 25, 2022. Municipal authorities in the Romanian capital, quoted by local media, stated that holiday season city light decoration levels will remain at last year's level and use energy saving solutions. (Photo by Vadim Ghirda/AP Photo)

Two men try to load their just purchased Samsung 55" TV into a car, at a Best Buy store in Fairfax, Virginia on November 26, 2015, on a Black Friday sale that started a day earlier during Thanksgiving evening. The US holiday shopping season kicks off with "Black Friday" – the day after the Thanksgiving holiday – with a frenzy expected at stores around the country as retailers slash prices. (Photo by Paul J. Richards/AFP Photo)

An Ultra-Orthodox Jewish man uses a stick to to separate the wheat grains in the Ultra-orthodox moshav of Komemiyut May 3, 2016. The harvested wheat will later be used to make the traditional unleavened bread eaten during the Jewish holiday of Passover. (Photo by Amir Cohen/Reuters)