An assailant armed with a rifle has shot and wounded a guard inside Washington DC's Holocaust museum before being wounded in turn, city police say.
Both have been taken to hospital where their condition is unknown, a police spokeswoman told the Associated Press.
No details were given of the "shooter" other than that a rifle was used.
Located on the US capital's National Mall, the Holocaust Memorial Museum is a national institution visited by 30 million visitors since opening in 1993.
Reports suggest a third person was also hurt but it is unclear if the injuries were caused by gunfire or broken glass.
Roads surrounding the museum have been closed.
Students on a school trip heard several gunshots before they were evacuated from the building, the mother of a Massachusetts teenager told the Associated Press.
Sandy Perkins said her daughter Abigail had called her shortly after the shooting.
Some of her friends were very shaken but all were otherwise fine, the mother said.
None of the children saw where the shots were coming from before they were safely evacuated to buses outside the museum.
The museum normally has a heavy security presence with guards positioned both inside and outside.
All visitors are required to pass through metal detectors at the entrance, and bags are screened.