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)

Adrienne Sipe (L) and Brooke Gilliam of Washington D.C. leap off a snow podium they made near the U.S. Capitol in Washington February 13, 2014. A deadly and intensifying winter storm packing heavy snow, sleet and rain pelted a huge swath of the U.S. East Coast on Thursday, grounding flights and shuttering schools and government offices. (Photo by Kevin Lamarque/Reuters)

The solar eclipse is seen above the Washington Monument on April 08, 2024 in Washington, DC. People have traveled to areas across North America that are in the “path of totality” in order to experience the eclipse today. The next total solar eclipse that can be seen from a large part of North America won't happen until 2044. (Photo by Chip Somodevilla/Getty Images)

A hot air balloon floats over farm fields south of Washington, Ill., as the sun slips behind clouds on the autumn afternoon of Wednesday, September 24, 2014. (Photo by Ron Johnson/AP Photo/Peoria Journal Star)

A Southwest Airlines jet takes off from Reagan National Airport with a thunderhead to the east on June 20, 2017 in Alexandria, VA. (Photo by Jonathan Newton/The Washington Post)

A couple walks across the Francis Scott Key Bridge as the setting sun lights up the clouds in Washington, Friday, October 30, 2020. (Photo by J. David Ake/AP Photo)

U.S. President Donald Trump holds news conference on the coronavirus outbreak at the White House in Washington, U.S., February 26, 2020. (Photo by Carlos Barria/Reuters)

As an airliner prepares to land, a bird takes off at the Gravelly Point park near Reagan National Airport in Arlington, Va. on December 23, 2018. (Photo by Michael S. Williamson/The Washington Post)