Law enforcement officials, speaking with news services on condition of anonymity, identified the gunman as James W. von Brunn. News organizations widely reported that von Brunn took out a .22 caliber rifle outside of the security checkpoint at the entrance of the museum and opened fire.
Listen to Kwame Holman's report on the shooting.
Washington Police Chief Cathy Lanier said the gunman was "engaged by security guards immediately after entering the door" with a rifle. "The second he stepped into the building he began firing."
Shot immediately was Stephen Johns, a six-year veteran of the museum's security service. Johns was transported to a hospital, but died from his wounds.
Von Brunn was critically wounded when other guards returned fire and officials said the suspect never made it past the security checkpoint.
Media reports about von Brunn portrayed a man who wrote a book alleging a Jewish "conspiracy to destroy the white gene pool." In 1983, he was also arrested for a plot to kidnap members of the Federal Reserve Board.
Organizations that track white supremacist Web sites said that von Brunn was a relatively well-known racist who lived in Maryland. Within hours of the shooting, FBI agents were reportedly searching his home in Annapolis, Md., and were seen taking his computer out of his home.
Witnesses described a chaotic scene as hundreds of schoolchildren and tourists fled the shooting.
"We had to sprint as fast as we could out the door," the Associated Press quoted 14-year-old Ashley Camp as saying. "I thought it was [part of an exhibit], but then everyone started screaming and running."
By late in the day Wednesday, the museum had confirmed the death of the guard, saying, "Our thoughts and prayers go out to Officer Johns' family."
"Officer Stephen Tyrone Johns died heroically in the line of duty today," read a statement from the U.S. Holocaust Memorial Museum released Wednesday afternoon. "There are no words to express our grief and shock over these events."
The museum announced it would also be closed on Thursday and the flag flown at half-staff in memory of Johns.
At the White House, just blocks away from the museum, President Barack Obama said, "This outrageous act reminds us that we must remain vigilant against anti-Semitism and prejudice in all its forms. No American institution is more important to this effort than the Holocaust Museum, and no act of violence will diminish our determination to honor those who were lost by building a more peaceful and tolerant world."
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