“If starting a race war is what this kid is about, he did it in the worst possible way,” said Kirk Lyons, a prominent lawyer who has defended Ku Klux Klan members, supporters of the old southern Confederacy and a notorious Holocaust denier.

“I’m a Christian,” Lyons added. “I consider the congregants of black churches my fellow Christians. These are the last people you want to hurt.”

On far-right online comment forums, avowed white nationalists and white supremacists substantially agreed, worrying that the Charleston killings might become an excuse for the government they hate to arrest them, crack down on gun ownership and suppress public displays of the Confederate flag many of them revere.

“More bad news for nationalism, no matter his political beliefs,” one poster, using the name Defend Our Homeland , wrote on the white supremacist site Stormfront.

The available evidence suggests some stark differences between Roof, a troubled kid with no known history of affiliation with extremist groups, and McVeigh, a decorated army veteran who steeped himself in politics on the gun show circuit for more than two years, knew most people in the movement and planned the bombing over a period of months.

On Saturday an online manifesto , on a website created in February by a registrant who listed his or her name as Dylann Roof and which contained photographs of Roof posing with a gun and Confederate flags, was being investigated by the FBI and Charleston police.

The statement, the authorship of which was not confirmed, was filled with racial invective, especially against black people, and laid out plans to strike in Charleston, a city that was majority black at the time of the civil war and has remained at the centre of America’s tortured racial history since. But the document did not give any indication of a broader political agenda, dwelling instead on lines from the violent Japanese teenage rebellion movie Himizu and a belief that the author needed to act because nobody else would.

Lyons, who ran in circles only a remove or two away from McVeigh in the 1990s, said Roof had no profile in the movement.

“Nobody as far as I know knows anything about this guy,” he said. “He’s just one of those kids our generation has a bad habit of turning out.”

Ben Jones of the Sons of Confederate Veterans - a one-time actor who appeared on the TV show Dukes of Hazzard - wasted no time denouncing the Charleston killings as “an act of purposeful evil”. He added: “We must not allow the sickness of one demented individual to become that with which the media and our ‘politically correct’ opponents define us. We are the same good-hearted people that we were last week and last year.”

Whether Roof turns out to have been a lone wolf or just a loner - “well down the path of nuttiness”, in the words of Kirk Lyons - his actions have already activated the far-right’s propensity for paranoid thinking. The Charleston killings have spawned very similar conspiracy theories to those that circulated after the Oklahoma City bombing about government “false flag” involvement - the theory being that the federal government wanted an excuse to crack down on militias and pass more stringent gun laws.

One much-forwarded comment on Vanguard News Network this week read: “The whole thing smells of psy-ops.” Even Lyons said he detected a “Manchurian candidate-ness” to the attack on the Emanuel AME church.

“Where do these guys come from, all over-medicated and weird looking?” he said. “I’m just wondering what’s going on here … There’s a lot of people in the system that benefit from racial antagonism.

“I don’t know - I don’t have any evidence. But the conspiracy nut in me thinks there’s maybe something.”