A Black Hawk helicopter crashed onto a golf course in Maryland during a routine training flight, killing one crew member and injuring two others, the US Army said.
The cause of the crash is under investigation, the US Army Military District of Washington said.
"We are deeply saddened by this loss within our community," said Major General Bradley Becker, commanding general, Joint Force Headquarters National Capital Region and the US Army Military District of Washington.
Three crew members were aboard the UH-60 Blackhawk. The Army said one person is in serious condition and one is in critical condition.They are being treated at the R Adams Cowley Shock Trauma Centre at the University of Maryland Medical Centre in Baltimore.
They were not identified, pending notification of relatives.
The aircraft was from the 12th Aviation Battalion, stationed at Davison Airfield, Fort Belvoir, Virginia.
Kevin Bowen, who works in the pro shop of the Breton Bay Golf and Country Club, said he saw the helicopter "flying kind of low" and then "saw it spinning" before it went down between the third and fourth holes of the course in Leonardtown, 97 km southeast of Washington, D.C.
Dorothy Harper, who lives across the street from the golf course, said she saw the helicopter just before it crashed.
"I was outside in my front yard when I saw the helicopter come over right across the street from my house. I saw pieces actually falling off the helicopter," she said.
Harper said she didn't see smoke or flames, "just pieces falling out of the sky".
Shortly afterwards, emergency vehicles started rolling in, she said.
Army investigators were driving around the course in golf carts, placing evidence markers near pieces of debris.
A team from the Army Combat Readiness Center, in Fort Rucker, Alabama, will be on site Tuesday to conduct the investigation, the Army's statement said.
The incident comes less than two weeks after a military jet crashed in a wooded area just outside a suburban Washington neighbourhood. The pilot, who was on a training mission, ditched his jet. He was treated for minor injuries, and no one else was injured in that incident.