New details have emerged about the U.S. Army Black Hawk helicopter that collided with an American Airlines regional jet over Washington, D.C.,

late Wednesday night, sending both aircraft plunging into the Potomac River. According to Defense Secretary Pete Hegseth, the military helicopter was conducting a continuity of government mission—an exercise tied to national security and emergency preparedness.

American Airlines flight 5342, which had 64 people on board and departed from Wichita, Kansas, went down near Ronald Reagan Washington National Airport after striking the UH-60 Black Hawk. The three soldiers aboard the helicopter, a captain, a staff sergeant, and a chief warrant officer, were also killed, according to the Pentagon.

Hegseth described the Black Hawk’s flight as part of a “routine annual retraining of night flights on a standard corridor,” raising immediate questions about why a highly sensitive military mission was operating in such close proximity to civilian air traffic.

“Tragically, last night, a mistake was made,” Hegseth explained.

“We do know on our side who was involved. It was a fairly experienced crew, and that was doing a required annual night evaluation,” Hegseth said earlier. “We anticipate that the investigation will quickly be able to determine whether the aircraft was in the quarter at the right altitude at the time of the incident.”

“It’s a tragedy, a horrible loss of life for those 64 souls on that civilian airliner. And of course, the three soldiers in that Black Hawk. They’re in our prayers, their families and their communities as people are notified.”