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)

As the sun rises, Gentoo penguins start their day on Wednesday, February 17, 2016, on Sea Lion Island, Falkland Islands. Sea Lion Island, which lies about 10 miles to the south of mainland East Falkland, is the southern most human-inhabited island of the more than 750 islands and islets of the Falkland Islands. (Photo by Jahi Chikwendiu/The Washington Post)

A sculptural artwork creation is displayed as part of the “Fashion in Motion: Daniel Lismore” exhibition by British multidisciplinary artist Daniel Lismore, at the Victoria and Albert Museum in London, Britain on August 5, 2022. (Photo by Toby Melville/Reuters)

A young woman dressed as a zombie takes part in a zombie parade as part of the Brussels International Fantastic Film Festival 2014 in Brussels, Belgium, 12 April 2014. More than a hundred of participants took to the streets of Brussels. (Photo by Ulien Warnand/EPA)

The best man in a wedding party, who all declined to be identified, stands near the bride and groom as he holds an AR-10 rifle he was handed while the party was having their pre-wedding portraits taken on the steps of the capitol before a rally nearby by gun-rights advocates to protest a new expanded gun background check law in Washington state Saturday, December 13, 2014, in Olympia, Wash. The wedding party was not part of the protest, but posed for pictures with it after being handed it by gun activist Brandon Lyons, who said “we've all just broken the law”, by handing the gun over. Saturday's protest was called the “I Will Not Comply” rally, and those attending said they will openly exchange firearms in opposition to the state's new voter-approved universal background check law, Initiative 594. The law, which took effect on December 4, requires background checks on all sales and transfers, including private transactions and many loans and gifts. (Photo by Elaine Thompson/AP Photo)

A dragster supercharger hits cameraman Joe Rooks of Bowling Green, Ohio, in the back at the U.S. Nationals N.H.R.A. drag races in Indianapolis, Indiana, on Saturday, September 1, 1979. Rooks was knocked flat by the heavy blower from a dragster that turned over and disintegrated near Rooks. Rooks died en route to the hospital. (Photo by Chuck Robinson/AP Photo)

A new species of monkey found in the Democratic Republic of the Congo and identified as Lesula (Cercopithecus lomamiensis) is seen in this undated photograph from an article published September 12, 2012 in the science journal PLOS One. The monkey was first seen in 2007 by researchers John and Terese Hart of the Peabody Museum of Natural History at Yale Research Project. The finding of C. lomamiensis represents only the second new species of African monkey to be discovered in the past 28 years, according to the research article. (Photo by Hart J. A., Detwiler K. M., Gilbert C. C./Reuters)