Yet there's scant evidence the Army veteran and retired trucker with Ku Klux Klan links ever resorted to violence before Sunday, when authorities say Cross - armed with a shotgun and pistol - opened fire outside two Jewish sites near Kansas City. None of the three people killed turned out to be Jewish.
The 73-year-old, who shouted a Nazi slogan at television cameras when arrested minutes later, is jailed awaiting charges that investigators said could come as early as Tuesday. At some point, a federal grand jury is expected to review the slayings, which investigators now deem a hate crime.
"We want to express our condolences to the families of these poor souls who happened to be in the wrong place at the wrong time and had the unfortunate experience of a first-hand encounter with evil," U.S. Attorney Barry Grissom said.
The FBI and police have not offered any public explanation for what triggered Sunday's deadly outburst in Overland Park on the eve of the Jewish festival of Passover. While the FBI and other law-enforcement agencies were familiar with Cross, Sunday's gunfire was "very quick" and "very random," the FBI's Michael Kaste said.
"We don't really see how this could have been prevented. There's at least no obvious answer," said Mark Potok, a senior fellow at the Alabama-based Southern Poverty Law Center, which tracks hate groups and had a considerable dossier on Cross. "He is one of the more frightening characters out there, no question about that."
A Johnson County jail official reached Monday by The Associated Press refused to make Cross available and referred inquiries to his attorneys and Overland Park police. The Kansas Star reported that Cross had been assigned two federal public defenders.
Knocks by an Associated Press reporter went unanswered Monday at Cross' small, single-story home bordered on three sides with barbed-wire fences near the southwest Missouri town of Aurora, some 180 miles south of Overland Park. Parked outside was a red Chevrolet bearing two Confederate flag stickers.
The Southern Poverty Law Center said Cross, who also went by the name Frazier Glenn Miller, has been immersed in the white-supremacist movement most of his life. During the early 1980s, Cook was "one of the more notorious white supremacists in the U.S.," according to the Anti-Defamation League.
He founded the Carolina Knights of the Ku Klux Klan and served as its "grand dragon" before launching the supremacist White Patriot Party, the law center said.
By 1987, he was the target of a nationwide manhunt for violating terms of his bond while appealing a North Carolina conviction for operating a paramilitary camp. Federal agents tracked him down along with three other men to a rural Missouri mobile home stocked with hand grenades, automatic weapons and thousands of bullets.
A federal grand jury indicted Cross on weapons charges and accused him of plotting robberies and the assassination of the law center's founder, Morris Dees. He then served three years in federal prison. As part of a plea bargain, Miller testified against other Klan leaders in a 1988 sedition trial.
Cross, using the name Frazier Miller, ran for the U.S. House in 2006 and the U.S. Senate in 2010, each time espousing a white-power platform.
During his Senate run as a registered write-in candidate, Cross' effort to air anti-Semitic ads was scuttled by the Federal Communications Commission, which concluded Cross was not a "bona fide" candidate entitled to mandatory access to the state's broadcast airwaves. The ruling allowed Missouri broadcasters to reject Miller's ads, such as one that urged white people to "unite" and "take our country back." It also criticized immigrants and minorities.
At the time, Miller complained in a written statement that the FCC action "deliberately silenced my political campaign" and made it "absolutely impossible for me to get elected." He responded to an AP telephone interview request with anti-Semitic slurs and profanity.
Violence ultimately proved fatal to his son. Jesse Miller was 30 and wielding a shotgun in 2008 when he was shot and killed by a police officer he wounded in southwestern Missouri's Marionville. The confrontation happened moments after Jesse Miller had gunned down a passer-by who stopped to help him after a car crash.
It was never clear what motivated the younger Miller to resort to gunfire.
In Cross' southwestern Missouri hometown Monday, most locals approached by the AP waved off the opportunity to discuss the man authorities suspect killed 69-year-old Dr. William Lewis Corporon and his 14-year-old grandson, Reat Griffin Underwood, outside the Jewish Community Center of Greater Kansas City. Both were Christians killed moments before Terri LaManno - a 53-year-old Catholic occupational therapist and mother of two - was gunned down outside a Jewish retirement complex where she was visiting her mother.
"It was bound to happen. You can't be that deep into what he was into and not expect something to happen," said Steven Roberts, who lives in Aurora, a roughly three-hour drive from Overland Park.
Cross was well-dressed and educated, Roberts said, but "just had a deep hatred for other races."
In nearby Marionville, population 2,200, Mayor Dan Clevenger said Cross often distributed racist pamphlets around town.
"He's gone overboard," Clevenger said. "He's way too carried away with his ideas."
Associated Press Writer Bill Draper contributed to this story in Overland Park, Kan.