WASHINGTON - An 88-year-old gunman known to authorities as a white supremacist fatally shot a security guard at the U.S. Holocaust Memorial Museum in downtown Washington yesterday before being wounded by guards who returned fire, officials said.

The security guard, who was identified by police as Stephen Tyrone Johns, 39, of Temple Hills, Md., and the gunman were taken to George Washington University Hospital.

Johns, who suffered a gunshot wound to the chest, died at the hospital, authorities said. The suspect underwent surgery and was in critical condition last night. He was shot in the face, with the bullet exiting his neck.

Museum officials said in a statement that Johns had worked at the museum for six years. The museum said it would be closed today and would lower its flags to half-staff to honor Johns' memory.

President Obama condemned the shooting, which he said underscored the need for vigilance against anti-Semitism.

A law-enforcement source identified the gunman as James W. von Brunn. On an anti-Semitic Web site he apparently maintained extolling a "Holy Western Empire," von Brunn wrote that he served in the Navy during World War II, worked for 20 years as an advertising executive and film producer in New York, and then became "an artist and author" living in Maryland.

In 1983, he was sentenced to prison for trying to kidnap members of the Federal Reserve Board of Governors out of anger over high interest rates.

A woman who opened the door at von Brunn's apartment, in a neighborhood outside downtown Annapolis, Md., declined to comment.

Police recovered a notebook from the gunman that apparently contained a list of Washington locations, including Washington National Cathedral, law-enforcement sources said. Police bomb squads were called to search and secure those locations after the shooting, including one in the 1400 block of Pennsylvania Avenue near the White House.

A law-enforcement official said that von Brunn also was carrying a list he had made of lawmakers on Capitol Hill, the Associated Press reported.

In a statement issued by the White House, Obama said: "I am shocked and saddened by today's shooting at the U.S. Holocaust Memorial Museum. This outrageous act reminds us that we must remain vigilant against anti-Semitism and prejudice in all its forms."

He praised Johns as "a courageous security guard who stood watch at this place of solemn remembrance" and said his thoughts and prayers were with Johns' family and friends.

Last week, Obama visited the Buchenwald concentration camp in Germany, where an estimated 56,000 people died, and issued a public challenge to "those who insist the Holocaust never happened." He described the camp as "the ultimate rebuke to such thoughts, a reminder of our duty to confront those who would tell lies about our history."

Sen. Frank R. Lautenberg (D., N.J.), who serves on the board of the museum, said: "We are horrified by what happened in Washington today. It is especially shocking that this attack took place at a museum designed to prevent violence and remind us of the dangers of hatred and bigotry."

In Philadelphia, officials at the National Museum of American Jewish History, on North Fifth Street at Independence Mall East, asked city police to increase patrols in the area.

Sgt. David Schlosser, a spokesman for U.S. Park Police, said the guard and the gunman were the only two hit by gunshots. An unidentified victim with less serious injuries was also taken to the hospital.

A spokesman for the museum, Andy Hollinger, said in a statement that after the gunman opened fire, "two museum security officers returned fire, hitting the assailant."

Details remained sketchy last night, but Johns apparently did not have time to draw his .38-caliber revolver before the shooter opened fire.

Police initially identified the attacker's weapon as a shotgun, but Washington Police Chief Cathy Lanier later said it appeared to be a rifle. Other law-enforcement officials told the Associated Press that it was a .22-caliber rifle.

The gunman "came into the entrance and immediately opened fire, striking one security guard," Washington Mayor Adrian Fenty said. "There was gunfire returned; the gunman was hit."

A spokeswoman for Wackenhut Services Inc. confirmed that the company provides security for the museum.

In a short biography on his Web site, von Brunn gave his birth year as 1920 and wrote that he held a journalism degree from a "mid-Western university."

He boasted in the Web biography and on a Wikipedia page of an escapade in which he attempted to take over the Federal Reserve on Dec. 7, 1981, holding the Board of Governors "under citizens arrest" and charging them with treason. He was captured, tried, and sentenced to 11 years in federal prison.

Upon his release after serving 61/2 years, von Brunn said, he joined Mensa, the society for people who score in the top 2 percent of a standardized intelligence test. An executive assistant at Mensa, Joy Martin, confirmed that von Brunn was a member for a year. But he was dropped from the membership rolls in 1988 for failing to pay dues.

According to the biography, von Brunn captained a PT boat in World War II and earned "four battle stars." That claim could not be immediately substantiated.

A leading U.S. Muslim organization, the Council on American-Islamic Relations, condemned "this apparent bias-motivated attack."

This article contains information from the Chicago Tribune.