WASHINGTON (CNN) -- The U.S. Holocaust Memorial Museum remained closed Thursday, its flags lowered to half-staff in tribute to a security guard gunned down by a man authorities identified as a rifle-wielding white supremacist.Later in the morning, the Metropolitan Police Department; the D.C. office of the FBI; the U.S. attorney's office and other federal and local officials will hold a news conference to discuss charges against the accused gunman, 88-year-old James von Brunn of Maryland.
The gunman entered Washington's crowded and solemn Holocaust museum on Wednesday afternoon and shot security officer Stephen Tyrone Johns. Other guards then shot and wounded the gunman, authorities said.
A six-year veteran of the museum's security staff, Johns later "died heroically in the line of duty," said Sara Bloomfield, director of the museum.
"Our thoughts and prayers go out to Officer Johns' family," the museum said.
Von Brunn is a Holocaust denier, well-known to human rights groups for decades, who created an anti-Semitic Web site called "The Holy Western Empire." The Southern Poverty Law Center, which focuses on human rights, said von Brunn has "an extremely long history with neo-Nazis and white supremacists."
He has repeatedly claimed "The Diary of Anne Frank," an iconic diary written by a teenage girl who was hiding from Nazis with her family, was a hoax. The guard died on the day the museum was to stage a play based on Anne Frank and two days before what would have been her 80th birthday.
Investigators found a notebook in the suspect's car listing other locations in Washington that he might have considered as targets, a federal official told CNN.
Von Brunn entered the United States Holocaust Memorial Museum at 12:50 p.m. Wednesday and immediately shot Johns with a rifle, said Chief Cathy Lanier of the District of Columbia's Metropolitan Police Department. Two other security guards returned fire, according to Lanier and the museum statement.
Sirens blared as emergency vehicles converged on the area, which is near the Washington Monument and other popular tourist attractions. The museum was full at the time, with a "couple of thousand" people inside, said William Parsons, chief of staff at the museum.
Von Brunn served six years in prison for trying in 1981 to kidnap Federal Reserve Board members because of high interest rates. He blamed his prison term on a "Negro jury, Jew/Negro attorneys" and "a Jew judge," he said on his Web site, "Holy Western Empire."
One of many questions is whether von Brunn, as a convicted felon, should have turned in his weapons or been barred from owning them.
The U.S. Park Police has asked the Bureau of Alcohol, Tobacco, Firearms and Explosives to trace the firearm, an effort that is expected to provide its original sale and ownership.
An FBI official said there was no warning or threat against the museum.
Both Johns and von Brunn were taken to George Washington University Hospital, said D.C. Mayor Adrian Fenty. Johns died at the hospital. Von Brunn was in critical condition, Fenty said.
Johns, 40, was a resident of Temple Hills, Maryland, according to a statement issued by Wackenhut Services Inc., which has provided security services at the museum since 2002.
"Obviously there are no words to express our grief and shock over the horrific event that took place at this museum today," Bloomfield, the museum director, said.
The Southern Poverty Law Center, which tracks hate groups, said von Brunn has "an extremely long history with neo-Nazis and white supremacists."
Witnesses to the shooting described blood on the floor and chaos within the museum's halls.
Visitor Maria Hernandez told CNN she heard five shots and saw the wounded security guard.
"It was definitely a security guard; he was down bleeding on the floor," said Hernandez, 19. "He was face down. His back ... blood was coming out."
Sirens blared as emergency vehicles converged on the area, which is near the Washington Monument and other popular tourist attractions. The museum was full at the time, with a "couple of thousand" people inside, said William Parsons, chief of staff at the museum.
"Never take your guard force and security people for granted," he said. "They did exactly what they were supposed to do to protect people in the museum."
Dave Pearson, a sixth-grade teacher in the Washington area, said he was on the museum's fourth floor when he heard a loud noise.
"At the time, we're visiting and all of a sudden there's like a boom, and all of a sudden they told us to stop where we're at," he told CNN. "Only thing we heard was a boom, and that was it."
The shooting sent shock waves throughout the nation's capital and elsewhere.
"I am shocked and saddened by today's shooting at the U.S. Holocaust Memorial Museum," said President Obama, who just days earlier had spoken emotionally about the Holocaust when he visited Buchenwald, a former Nazi concentration camp with Holocaust survivor and Nobel Peace Prize laureate Elie Wiesel.
"This outrageous act reminds us that we must remain vigilant against anti-Semitism and prejudice in all its forms," Obama said Wednesday. "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."
Israel issued a statement through its embassy, expressing sadness and condemning the attack.
The Anti-Defamation League said the shooting "reminds us in the starkest way where the spread of hatred can lead."
Happening "at the very place that was created to remember and teach about evil in the world," the attack "is an immediate reminder that words of hate matter, that we can never afford to ignore hate because words of hate can easily become acts of hate, no matter the place, no matter the age of the hatemonger."
The Council on American-Islamic Relations condemned "this apparent bias-motivated attack" and said it stands "with the Jewish community and with Americans of all faiths in repudiating the kind of hatred and intolerance that can lead to such disturbing incidents."
The museum canceled a performance scheduled for Wednesday night of a play about racism and anti-Semitism, based on a fictional meeting between Anne Frank and Emmett Till, the teenage victim of a racist killing in the United States.
Attorney General Eric Holder and Rep. Steve Cohen, D-Tennessee, were among those planning to attend the play, which was written by Janet Langhart Cohen, the wife of former Defense Secretary and U.S. Sen. William Cohen.
Langhart Cohen told CNN that Anne Frank's young life was ended by people filled with hate. She said it was hard to see that same hate manifest itself at this place of remembrance.
