Fox News identified the suspect as James W. Von Brunn. He is reportedly an elderly man tied to a white supremacy group. Police would not confirm the identity of the shooter. Fox says the man runs a Web site that espouses extremist views against Jews.

The D.C. police chief described the gun as a rifle and it appeared that the shooter acted alone.

Law enforcement sources told WTTG/MyFoxDC.com that during a search of a car that is believed to belong von Brunn, investigators found a notebook with information about six to nine locations in the D.C. area, including the National Holocaust Museum. Other locations on the list included the U.S. Capitol, the White House, the Washington Post, and a FOX News location.

Investigators followed up at each of the locations, trying to find out if there were any sightings of the suspect or any correspondence, MyFoxDC.com reported.

Mayor Adrien Fenty says the suspect is hospitalized in critical condition.