A gunman entered the lobby of the U.S. Holocaust Memorial Museum in Washington on Wednesday and shot a security guard shortly before 1 p.m., according to the U.S. Park Police.
A gun-battle followed in which security guards immediately shot the attacker, said Sgt. David Schlosser, a Park Police spokesman.
Metropolitan Police Department Chief Cathy Lanier said the security guards shot the gunman "immediately upon entering the door."
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Visitors described a chaotic scene inside the museum in which they heard multiple shots, then security guards screaming for them to get to the ground and take cover.
"We heard five shots," said Rosemary Floccari, 43, visiting from Akron, Ohio, for teachers' convention. "We thought it was part of an exhibit. Then we realized, it was real."
The security guard has been identified as Stephen Tyrone Johns, 39, who had worked at the museum for 6 years.
The shooter has been unofficially identified James W. von Brunn, of Annapolis, Md.
Click here for more on Mr. von Brunn.
Mr. von Brunn has a Web site holywesternempire.org that includes anti-Semitic and racial statements.
The site also states Mr. von Brunn has a journalism degree from a mid-Western university and served during WWII as a PT-Boat captain.
The site also states he was convicted of a crime in D.C. Superior Court and sentenced by a "Jew judge" to 11 years in prison. He served more than six years, purportedly for attempting to enter the Federal Reserve Board headquarters with a gun, upset over interest rates.
The museum is on the south edge of the city's downtown near the Potomac River and within blocks of the National Mall and its monuments. The area is a popular tourist destination in the Nation's capital, especially during the spring.
The victims were taken to George Washington University Hospital several miles northwest of the crime scene.
D.C. Mayor Adrian M. Fenty said the shooter is in critical condition.
A third victim was injured by flying glass. The person was treated and released at the scene.
Mr. Johns had worked at the Holocaust Museum as as guard for 6 years.
Investigators think the gunman acted alone and parked his vehicle outside the museum. They also said roughly 4,600 visitors were in the museum at the time of the attack.
Chief Lanier said bomb-detecting dogs are in the area, which is standard procedure after such an incident.
The museum opened in 1993 and since had more than 30 million visitors. Guards are positioned inside and outside and visitors are required to pass through metal detectors at the entrance and bags are screened, according to the museum's Web site.
Dianne Romano, 59, of Methuen, Mass., was on the museum's second floor with her husband, Danny, when they looked out a window and saw chaos outside the front doors.
"We saw people outside the building crawling under benches," she said. "Then someone walked up to us and said, 'Get away from windows. There's been shooting.' "
Mrs. Romano and a group of other tourists, who were near the end of the museum tour, decided to stay where they were.
"It was very scary," she said.
Mrs. Romano sent a text message to her daughter that read: "shootings. 911. Turn on the TV."
Moments later, museum staff came and rushed the Romanos out of the museum through a back entrance.
Once outside, police drove them halfway across the Mall away from the museum, Mr. Romano said.
"They were shoving and moving us across the Mall," he said. "Anytime we stopped they said to keep moving."
The roads around the museum, in the 100 block of Raoul Wallenberg Place Southwest, reopened late Wednesday afternoon, including the 14th Street Bridge, a major entrance-exit for Virginia commuters.
The museum will remain closed Thursday in honor of the officer, and flags will be flown at half-mast.
Reporters Jon Ward, Michelle Bollman, Jerry Seper, Melissa Giaimi and Michael Drost contributed to this story.