Scores of mourning staff members, Jewish community representatives and interfaith leaders gathered at the US Holocaust Memorial Museum on Thursday to stand against bigotry and hate and express support for the family of a security guard killed by a white supremacist a day earlier. Holding memorial candles and standing in somber reflection, the hundreds-strong crowd filled the courtyard of the museum in a vigil quickly organized by the Interfaith Conference of Metropolitan Washington following Wednesday's fatal attack. "As a interfaith community we have come together to show our disgust with such acts," declared Ari Rudolf of the Jewish Community Relations Council of Greater Washington. FBI agent Joseph Persichini made a similar point at a press conference held at the museum earlier in the day. "It is very important that we send a message that this country does not authorize or approve any act that is attached to hatred in America," said the assistant director of the District FBI field office. Law enforcement officials announced on Thursday they were charging the attack, James W. von Brunn, with murder and gun violations and that they were considering charging the 89-year-old white supremacist with hate crimes or civil rights violations. Persichini said investigators were searching Von Brunn's computer, home and car for evidence. While he acknowledged that there hadn't been any open investigations against Von Brunn, Pershichini said law enforcement had long been keenly aware of him. Von Brunn has claimed to be an associate of William Pierce, founder of the white supremacist group, the National Alliance. Von Brunn, who in 1999 published a book Kill the Best Gentile!, also ran an anti-Semitic Web site called "The Holy Western Empire," and in 1981 he was arrested for using a sawed-off shotgun to try to take hostages at the Federal Reserve Board on the grounds that Jews control America's banking system. He served six and a half years in prison. In 2008, the Southern Poverty Law Center designated his Web site as a "hate site." "He's been on our radar screen for decades," said Mark Potok, the director of the center's Intelligence Project. Jennifer Laszlo Mizrahi, founder and president of The Israel Project, said she warned local police about the National Alliance several years ago and expressed frustration that not enough had been done at that time. In December 2005, more than a dozen homes in Annapolis, Maryland - including Mizrahi's - were blanketed with anti-Semitic leaflets. An investigation connected the leaflets to the National Alliance, but prosecutors did not press charges because the leaflets were protected by the First Amendment. "The hands of the police department were tied," she recalled. "There was no legal recourse." Around the same time, a video promoting the Aryan race was aired for three nights on a local public access television station. At the time, county officials said they had no way to prevent the ads, which were protected by the First Amendment. "We checked everything to see if I had to legally allow them to proceed. I did," then-Anne Arundel County executive Janet S. Owens said at the time, calling the ad "anti-everything." Mizrahi said she could not be 100 percent sure Von Brunn had anything to do with leafleting her home, but she has little doubt. In 2005, a police officer told her the perpetrator was a "cranky old man" living in Annapolis. "I don't know how many cranky old men living in Annapolis are putting out absolutely vicious hate material on people's yards. I'd like to think there's not more than one," she said. She urged authorities to investigate the remaining members of his group, and said the lesson of Wednesday's attack should be clear. "The point is when people say we hate you, and we want to kill you, you need to take it seriously, whether it's a white supremacist group in Arundel County or Ahmadinejad in Iran," Mizrahi said. Still, Potok said such expressions were entirely protected by the First Amendment. "How might this man have been stopped? I don't have an answer for that," he said. Potok said, "The most important thing to learn from this attack is that this man was not some isolated sociopath on the fringe of the fringe of American society. He may indeed have been sick in the head, but he represents a very real, vibrant and apparently growing movement in this country." On Thursday, Washington Mayor Adrian Fenty expressed his condolences to the family of the museum guard, Officer Stephen Johns, who was killed in the attack. "One life lost is a tragedy, but this could have been much, much worse," he said. Jewish groups - whose buildings were fortified with extra security - responded to the shooting with a sense of shock, and sadness over the killing of Johns. "There is no shortage of hate in the world. But when it happens to you, your workplace, your family, your colleagues, it gets very painful," the chief of staff for the museum, Bill Parsons, said at a news conference. Earlier in the day, former US defense secretary William Cohen, who was at the museum during the shooting, spoke on national television and recounted seeing Von Brunn park his car and seconds later hearing gunshots. "It was pretty clear that they were gunshots," he said on CBS's Early Show. "It was fairly chaotic. As we went up the stairs, we didn't know if people were going to be following us up, whether there were more than one gunman." As he approached the stairs, he stopped a group of tourists who were about to leave the building. "Don't go there," Cohen recalled saying. "It's too dangerous." Those who came to the vigil on Thursday, though, said they wouldn't be made to feel afraid and would stand against those who tried to intimidate them. "I'm still going to wear a yarmulke. I'm still going to be Jewish," said Bruce MacIver, who works for the United Jewish Communities. He also said of the vigil, "I think it's a great showing to honor the slain officer and the Jewish community." Indeed, many members of the Jewish community tried to express support for Johns, 39. The American Jewish Committee announced that it was starting a fund to support the guard's family. The House of Representatives drafted a resolution condemning the shooting and praising Johns. Amid the outpouring of support, many at the vigil remained sobered by what had taken place at the museum just the day before. Harriet Fischel, an education volunteer at the museum, noted that usually she took pride in imparting knowledge to others. But on Thursday, she said, "The fact that it could happen there means we're not doing a good enough job."