He had given away his computer, and turned control of his Web site, www.holywesternempire.org, over to someone else, de Nugent said. The site is no longer accessible on the Internet.
"When you hear about people giving away precious things, it makes you think that something bad is going to happen," de Nugent said on "Good Morning America."
"I think at least a year ago, his Social Security was slashed. And he felt that this was a direct result of somebody in the federal government reading his Web site, and punishing him for his politically incorrect opinions," de Nugent said. "I think the election of Barack Obama became a tremendous signal of alarm for him."
"The FBI did not have an open investigation on Mr. von Brunn," said Persichini. "But we were aware of him, and he is known as an anti-Semite and a white supremacist that established Web sites that espoused hatred" against Jews, African-Americans and others.
Persichini said individuals who hold such beliefs are often acutely aware of their rights, and the type of activity or speech that would trigger an investigation.
"Law enforcement's challenge every day," he said, "is to balance the civil liberties of the United States citizen against the need to investigate activities that might lead to criminal conduct."
"No matter how offensive to some, we are keenly aware that expressing views is not a crime, and the protections afforded under the constitution cannot be compromised," he continued, stressing that investigators rely on tips in cases like von Brunn's.
"There has been a significant growth in white supremacist hate groups, on the order of something like 50 percent since the year 2000," director of the Southern Poverty Law Center's Intelligence Project Mark Potok said on"Good Morning America" today. "So, yeah, there is a heating up going on out there, and the Obama factor has been important."
Both de Nugent and the Southern Poverty Law Center, which tracks hate groups and their activity across the country, noticed an escalation in von Brunn's rhetoric.
"He was advocating direct action. That the time for talk was over," de Nugent said. "And I think he was pushed over the edge by current events and his own personality."
"His rhetoric really has been heating up. We've seen some evidence of that ourselves," Potok said, referring to a 2007 posting on a white supremacist site attributed to von Brunn that seemed to call for action.
The center said Wednesday that von Brunn had long been associated with neo-Nazis and Holocaust deniers. The group had also flagged his Web site because of its content.
The "politically incorrect opinions" on the site include excerpts of von Brunn's book, "Tob Shebbe Goyim Harog," or "Kill the Best Gentiles."
The book is described on the site as "the culmination of his life's work" and "a new, hard-hitting expose of the 'Jew Conspiracy' to destroy the White gene-pool."
The site also touted von Brunn's military and intellectual accomplishments. The U.S. Navy confirmed today that von Brunn served from 1943 to 1946. A Navy official said he earned several awards and decorations, including recognition for his WWII service.
On his Web site, von Brunn also claimed membership in high-I.Q. society Mensa. The organization confirmed that he was a member 20 years ago, but for less than a year.