Two people were shot Wednesday afternoon at the U.S. Holocaust Memorial Museum in Washington D.C.
The Washington police chief, Cathy Lanier said a man entered the building with what appeared to be a rifle and opened fire on an armed security guard.
The police chief said the guard and at least one other security officer returned fire. The first guard and the gunman suffered gunshot wounds and were transported to a hospital.
The mayor of Washington, Adrian Fenty says the security guard is in grave condition, while the suspected attacker is in critical condition.
News reports indicate the suspect is James von Brunn, who is in his late 80s and believed to have connections to white supremacist and neo-Nazi groups. But police have refused to confirm the attacker's identity.
A White House spokesman, Robert Gibbs said President Barack Obama is "saddened" by what happened and is monitoring developing information.
The Israeli Embassy in Washington, in a statement, condemned the attack, and said it is shocked and saddened by the shooting.
The FBI (Federal Bureau of Investigation) is working with local police on the investigation.
The Holocaust museum has been secured and evacuated. The building is next to the National Mall, in an area that is usually crowded with tourists and is not far from the White House.
Eyewitnesses tell television news service CNN that they heard at least five shots fired in the museum.