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)

Maj. Matt O'Donnell of Glenelg, MD shields himself from rotor wash as Ospreys carrying the delegation of U.S. Secretary of Defense Leon Panetta leaves on March 14, 2012 at Forward Operating Base Shukvani, Afghanistan. Panetta is also scheduled to meet with President Karzai during his two-day visit to Afghanistan. The trip comes as the Taliban has vowed revenge following this past weekend's killing spree by a U.S. soldier who is accused of killing 16 civilians in Afghanistan. Most of those killed were children and women. (Photo by Scott Olson/Getty Images)

People pose for photographs in the wind during Typhoon Saola in Tseung kwan O, in Hong Kong on Saturday, September 2, 2023. Typhoon Saola made landfall in southern China before dawn Saturday after nearly 900,000 people were moved to safety and most of Hong Kong and other parts of coastal southern China suspended business, transport and classes. (Photo by Billy H.C. Kwok/AP Photo)

Democratic presidential candidate and US Vice President Kamala Harris reacts as she holds a photographer's camera while flying on Marine Two, on her way to O'Hare International Airport, Chicago, Illinois, on August 20, 2024. Harris is traveling to Milwaukee, Wisconsin, to speak at a campaign event. (Photo by Kevin Lamarque/Pool via AFP Photo)

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)

These are the stomach-churning pictures of the swing at the end of the world – a rickety wooden swing hanging over a precipice 2,660 metres above sea level – and not a seatbelt in sight. (Photo by Caters News)

A woman in a wedding dress walks on the dried-up riverbed of the Jialing river, a tributary of the Yangtze, that is approaching record-low water levels in Chongqing, China on August 18, 2022. (Photo by Thomas Peter/Reuters)

Men rest on a boat in the overflowed Ganges River under the Shastri Bridge in Allahabad on August 17, 2022, as water levels of the Ganges and Yamuna rivers rose following monsoon rainfalls. (Photo by Sanjay Kanojia/AFP Photo)