He was "alienated, disaffected and angry", sociologist Pete Simi said.
While field doing fieldwork on hate groups, Simi, an associate professor of criminology at the University of Nebraska, befriended Page between 2001 and 2003 in Orange County in southern California.
Simi has written a book, "American Swastika: Inside the White Power Movement's Hidden Spaces of Hate", after interviewing dozens of other neo-Nazis and white supremacists as part of his research.
Milwaukee Journal Sentinel Thursday cited Simi as saying his recollection was that Page was a person who hated blacks and was anti-Semitic but never mentioned Sikhs.
"Blacks and Jews," Simi said. "Those were the primary targets of his rhetoric." After 9/11, Simi said Page sent him an email in which he expressed a lot of anger about Muslims.
"He said something like, 'America should just plaster all of the Middle East,'" Simi was quoted as saying.
As part of his research, Simi asked Page how he developed his hardcore beliefs. Page told Simi that as a young person in Denver, he fell in love with punk music and listened to it for hours on end. But punk music led to other genres. "He was aware of racist skinheads," Simi said.
But the real catalyst that turned Page into a neo-Nazi was his life in the military. Page served in the US Army from 1992 to 1998.
"He was exposed to hate literature in the military and met people in the military who were white supremacists," Simi said, adding he realised Page was like many neo-Nazis: alienated, disaffected and angry.
Citing an army buddy of Page, the Journal Sentinel said he was so mentally unstable after breaking up with a girlfriend that his Army friends once had to break into his apartment to make sure he had not committed suicide.
They found Page passed out from alcohol on the floor sometime in 1997, said Christopher Robillard, who served with Page at the time in the Army's elite psychological operations corps.
The incident is one of what must have been dozens of missed signals over the years, Jennifer Dunn, a psychiatric nurse who lived downstairs from Page in a Cudahy duplex for two weeks before the shootings, told the Journal Sentinel.