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 baby Black-crowned Night Heron squawks in its incubator while being cared for at City Wildlife rescue and rehabilitation center in Washington, DC on May 31, 2017. The heron is one of several that have been brought to CW by the staff at The National Zoo over the past few years. (Photo Linda Davidson/The Washington Post)

US Army Parachute Team Golden Knights perform a precision drop to commemorate the 50th anniversary of the end of the Vietnam War, above West Potomac Park in Washington, DC, USA, 11 May 2023. The performance is one of many activites being held on the National Mall over three days to honor Vietnam War veterans and their families and to commemorate the 50th anniversary of when the last US combat troops left South Vietnam in 1973. (Photo by Michael Reynolds/EPA/EFE)

A young girl tries to catch snow on her tongue near the Martin Luther King Jr. Memorial, before the start of a wreath-laying ceremony honoring the legacy of the late civil rights leader in Washington, DC on January 15, 2024. The ceremony is being held to honor the civil rights leader on the anniversary of his birthday. (Photo by Andrew Caballero-Reynolds/AFP Photo)

Actor George Clooney is arrested with his father Nick Clooney (2R) during a demonstration outside the Embassy of Sudan March 16, 2012 in Washington, DC. United to End Genocide, the Enough Campaign and Amnesty International held a rally to call on the United States and world leaders to stop the violence in South Sudan and prevent hundreds of thousands of people from starving. (Photo by Win McNamee/Getty Images)

Visitors review their cell phone photos of an installation called “Plexus A1” by artist Gabriel Dawe, one of nine large-scale art installations displayed at the “Wonders” exhibit at the Renwick Art Gallery in Washington, DC, Wednesday, January 13, 2016. Built in the 1860s, the Renwick was the first American building to be designed specifically as an art museum; it recently reopened after a two year renovation. (Photo by Jim Lo Scalzo/EPA)

A group of people walk on the sea wall as a man kayaks through the flooded parking lot in downtown Annapolis, Maryland, on October 29, 2021. The US National Weather Service implemented a flood watch for the cities of Baltimore and Annapolis as well as Anne Arundel, Baltimore and Howard counties. Washington, DC, and parts of Virginia faced the same alert. (Photo by Jim Watson/AFP Photo)

A man with an American flag on his back and a Biden/Harris campaign flag rides an electronic skateboard through Black Lives Matter Plaza in front of the White House on Election Day, November 3, 2020 in Washington, DC. This year's historic presidential election between President Donald Trump, the incumbent, and Democratic nominee Joe Biden begins to come to a close even though final results are not expected for days to come as states take longer to count historic levels of mail-in ballots. (Photo by Samuel Corum/Getty Images)