The Marine Corps was trying to confirm the center's information.
Ready's ex-wife, Arline Lindgren, knew that he had started associating with white supremacist groups when they were married in the late 1990s, her brother, Adam Lindgren, said. The couple divorced in 2003.
Lindgren said he got into a few arguments with Ready but that they were never violent. He said Ready had a temper, but "not a violent temper, that I was aware of." He said he never saw Ready be violent toward anybody.
Ready was "very, very opinionated. He would argue with you until ... well, just keep arguing with you," he said.
Ready was a member of the Detroit-based National Socialist Movement, whose members promote white separatism, dress like Nazis and display swastikas. It believes only non-Jewish, white heterosexuals should be American citizens and that everyone who isn't white should leave the country "peacefully or by force."
Ready first tried to get into politics in 2004, when he unsuccessfully ran for a seat in the Arizona House. In 2006, he lost a run for Mesa city council but was later elected as a Republican precinct committeeman.
He didn't run for re-election in 2008 after three Republican congressmen wrote a letter to a GOP county chairman asking for his removal because of his neo-Nazi ties. They said Ready was sullying the party's image. They said he was a featured speaker at a neo-Nazi conference in Omaha, Neb., in September 2007 and distributed racist and anti-Semitic literature at a GOP meeting.
Trying to distance himself from the movement, Ready told The Arizona Republic in 2010 that he left the group. Potok said the move was "merely for cosmetic reasons."
Ready was also running his desert operations targeting illegal immigrants, one of which was featured on the National Socialist Movement's website as recently as January. Some of the photos on the website match ones posted to his Facebook page.
They include images of Ready and other members wearing head-to-toe camouflage gear, helmets and boots, and carrying high-powered guns during a weekend operation ending Jan. 29. The group claimed to help the U.S. Border Patrol apprehend one illegal immigrant.
"Some of us have our fingers on the triggers," Ready wrote in a post on a website for his group. "Soap box. Ballot Box. Ammo box. These were given to us by our founding fathers and mothers. We have just about depleted the first two options."
In January, Ready announced that he wanted to become sheriff in Pinal County. Ready listed himself as a Democrat, and most considered his chances of being elected laughable.
Former Arizona Rep. Russell Pearce, the chief architect of some of the state's tough legislation against illegal immigrants, was once Ready's political ally and friend, but said in a statement that he distanced himself after learning of his ties to white supremacists.
"At some point in time, darkness took his life over," he said.
Associated Press writers Terry Tang in Gilbert, Ariz., Michelle Price in Phoenix and Carson Walker in Maricopa, Ariz. contributed to this report.