The gunman has been identified as James Von Brunn.
Looks like he had is issues:
According to NBC, the man who shot a security guard and potentially one to two other people at the Holocaust Museum today is 89-year-old James W. Von Brunn. Von Brunn maintains a white-supremacist Web site, HolyWesternEmpire.org. The biography of Von Brunn on the site states that he spent over six years in federal prison for attempting to “place the treasonous Federal Reserve Board of Governors under legal, non-violent, citizens arrest.” A World War II veteran and resident of Maryland, Von Brunn is the author of a pamphlet entitled “Kill the Best Gentiles: A new, hard-hitting exposé of the JEW CONSPIRACY to destroy the White gene-pool.” He is a Holocaust denier who has written that “Hilter’s worse mistake” was that “he didn’t gas the Jews.”