A gunman believed to be linked to an anti-Jewish website has shot a security guard at the United States Holocaust Memorial Museum in Washington.
US media have reported that the guard died from his injuries after being rushed to hospital following the attack.
Officials say the elderly gunman was wounded when guards returned fire and is in a critical condition in hospital.
A federal law enforcement official said investigators had identified James W. von Brunn and linked him to a website that expresses anti-Government and anti-Jewish sentiments.
Stephanie Geraghty, 28, who had been visiting the museum, said the shooter appeared to be a white male carrying a silver gun.
The museum is a memorial to the 6 million Jews killed by Nazis in the Holocaust and is near the National Mall where many of Washington's monuments are located.