Dylann Roof, the alleged shooter in the Charleston, S.C., church massacre, was the architect of his own radicalization, drawing from the deep well of online hate to transform himself into a lone wolf domestic terrorist, according to law enforcement officials and experts on the white supremacy movement.

Roof, 21, appears to have traveled along a well-trod digital network of white nationalist Web sites — a path that has attracted thousands of white Americans to places where they can anonymously rail against blacks and Jews, but a route that rarely ends in violence.

The paradox of racist extremism in the Internet age is that there are more white supremacist groups and sites than ever before. But the average size of each group is smaller than it’s been in decades and the groups’ ability to organize beyond online comment boards has diminished greatly, according to government and private investigators who monitor the movement.

The rise of the self-taught extremist has put investigators in a bind: White racist groups are less capable of producing organized violence, but the attacks that do develop come mainly from solo actors whose paths to violence are far more difficult to track.

“A lot of these guys are all talk and no show,” said David Gomez, a retired FBI agent who investigated supremacist groups for three decades and ran the counterterrorism task force in Seattle. “These are guys with anger issues about race and unfairness and loneliness and inadequacy, and they find this stuff online and start copying the rhetoric. Instead of meeting in a hall somewhere, they meet in chat rooms and form very small, clandestine cells of three or four people. They’re much harder to infiltrate, and most of them never do anything but talk.”

Dylann Roof is in custody after police say he opened fire at a historic African American church in Charleston, SC. Here’s a look at the 21-year-old's background, including recent arrests, and what authorities say happened inside the church. (Alice Li/The Washington Post)

A survey of U.S. law enforcement agencies by researchers at the University of North Carolina and Duke University released this week reports that 74 percent listed right-wing extremism, including white supremacist groups, as one of the top terrorist threats in their communities, almost twice as many as those who put Islamist threats in that category.

But several recent attacks — such as the 2012 shootings at a Sikh temple in Wisconsin and last year’s attacks outside Jewish centers in Kansas — have been launched not by groups, but by self-radicalized individuals whose capacity for extreme violence had not been caught in time.

The extremist groups’ leaders themselves agree that they have largely lost the ability to move from rhetoric to action for two reasons: They have been neutered after years of infiltration and monitoring by the FBI and private groups such as the Anti-Defamation League, the Simon Wiesenthal Center and the Southern Poverty Law Center. And the movement’s migration into a digital world, where followers are largely anonymous, has made it harder to bring people onto the streets.

“Even when the underlying rage is there about race, it’s become difficult to get people to demonstrations,” said Don Black, founder of Stormfront, the largest supremacist site. “Anonymity is a double-edged sword: It allows people to express views in relative safety, but many people consider that to be their activism, in lieu of going out and taking a stand.”

“We talk about this at our board meetings all the time: It’s hard to motivate grass-roots activists to get out of their chairs and away from their screens,” said William Johnson, chairman of the American Freedom Party, a Los Angeles-based group that bills itself as “a nationalist party that shares the customs and heritage of the European American people.” “This is causing great concern to us.”

Johnson, a lawyer who advocates creating a “white ethno-state” in the United States, agrees with investigators that the bulk of the action emerging from the extremist movement in coming years will stem from lone wolf attacks such as the Charleston shootings.

“There’s very little the FBI stands for or says that I agree with, but they’re exactly right about this,” he said.

Private groups that track extremists have hundreds of white supremacist Web sites and organizations on their radar, a number that spiked after President Obama was elected, according to tallies by private and federal investigators.

Many of those sites are one-man operations, and many of their followers have only anonymous contact with fellow radicals. FBI Director James B. Comey said last year that “we face a continuing threat from homegrown violent extremists [who] are self-radicalizing. . . . They are willing to act alone, which makes them difficult to identify and stop.” A senior law enforcement official in South Carolina said the emerging evidence is that Comey’s description applies to Roof’s journey to Emanuel AME Church in Charleston.

The only site on which evidence of Roof’s activity appears to have been found is the Daily Stormer, a nationalist blog by Andrew Anglin, a 30-year-old American who, according to his father, lives in Asia. Greg Anglin, the father, is a Christian counselor in Ohio, and he said that his son, like Roof, found his way to his supremacist views on his own. (Andrew Anglin did not respond to messages seeking comment.)

Greg Anglin, who said he is “not really involved with Andy’s site” even though it was registered in his name, said that “Andy does what Andy does.”

“If there’s things I disagree with him on, I sit down and talk with him directly rather than airing it in public,” he said.

The generation of supremacists who led groups in the 1990s “is pretty much gone,” said Rabbi Abraham Cooper, associate dean of the Simon Wiesenthal Center, which tracks extremist groups. “They’ve been replaced by online organizations that look to inspire lone wolves by creating a sense of empowerment, a sense of community.”

Shifting social attitudes have also altered white supremacists’ tactics and rhetoric. As overt racism has become less socially acceptable, “the most prominent white nationalists these days have moved away from violence,” said J.M. Berger, who researches extremist activities in the United States for the Brookings Institution and Intelwire.com, his Web site. “They generally recognize that their views are repugnant to most people, so they’re less visible and prominent. Posting pseudonymously is generally safer and more comfortable than trying to assemble a meeting.”

Along the trail

White supremacists have a noticeable foothold in the real world where Roof lived, in Lexington County, S.C., a sprawling region with great wealth and dire poverty. One of the largest white nationalist groups, the Council of Conservative Citizens, is active in the county. The Southern Patriot Shop, a repository of extremist literature and Confederate paraphernalia, is in Abbeville, 70 miles to the west.

The shop’s owner, Robert Hayes, a member of the League of the South, which pushes for an independent, Christian Southern republic run by an “Anglo-Celtic” person, condemned the Charleston shootings. “There’s no call for violence,” he said, and then he paused. “Unless you are defending yourself. The Southern people had to become violent because we were invaded.”

Despite the presence of organized supremacists, Roof — who sometimes slept on a sheetless mattress on the floor of a mobile home where a friend from middle school lived — came to his virulent ideology on his own, according to investigators and friends. There’s no indication he met with or joined any groups.

The friend Roof stayed with, Joey Meek, and others in the house said he always called black people “African Americans” and once said he admired Jackie Robinson even though he doesn’t care for baseball. Roof was an often-silent, awkward housemate who liked to watch “Oprah” during the day and loved sappy movies such as “Titanic” and “Stand By Me.”

Meek’s brother Justin said Roof spent a lot of time on his smartphone, doing more reading than typing. Justin, 17, noticed a couple of months ago that Roof had put a Confederate flag decoration on his front license plate, but that didn’t especially stand out in the Columbia area. And Meek said Roof’s friendship with a black neighbor, Christon Scriven, was “normal and cool.”

But “the Trayvon Martin case made him flip out,” said Jacob Meek, youngest of the three brothers. Lindsey Fry, 19, Joey Meek’s girlfriend, recalled Roof saying that the shooting of Martin, an unarmed black teen killed by a neighborhood watch volunteer in Florida in 2012, marked “the start of America’s race war.”

Roof, who remains jailed on nine murder counts, wrote about making racial jokes as far back as high school — he quit school after repeating ninth grade — but it wasn’t until after the Martin shooting that he “typed the words ‘black on white crime’ into Google, and I have never been the same since that day. The first website I came to was the Council of Conservative Citizens. There were pages upon pages of these brutal black on White murders.”

By this year, Roof had concluded that he had to step out from the cloak of the Internet and do something. “We have no skinheads, no real KKK, no one doing anything but talking on the internet,” he wrote. “Well someone has to have the bravery to take it to the real world, and I guess that has to be me.”

Portions of the language he used in the manifesto appear word for word under the pseudonym AryanBlood1488 in comments on the Daily Stormer. Fourteen is a commonly used code number in supremacist circles, referring to a 14-word slogan attributed to David Lane, a prominent white separatist leader who died in prison in 2007: “We must secure the existence of our people and a future for white children.” And 88 is a widely used reference to Adolf Hitler; the 8s may represent the eighth letter in the alphabet, H, as in “Heil Hitler,” or an 88-word passage in Hitler’s “Mein Kampf” that rallies followers to “safeguard the existence and reproduction of our race.”

One of the authors of the Council of Conservative Citizens’ diatribes about African Americans, Kyle Rogers, lives in Summerville, S.C., outside Charleston. In an interview, Rogers said he never met or communicated with Roof. Blaming the group for Roof’s radicalization would make no more sense than blaming Wikipedia, he said.

Rogers called the church killings abhorrent and said Roof deserves to be executed. “The kid was damaged goods,” he said.

Same beliefs, new etiquette

Violence, many white supremacists say, is not how they plan to win. Rather, they say that whites who become fed up with crime, disorder and a country that seems to be slipping away from them will rally to the cause of racial separation.

“This guy was obviously very disturbed,” said James Edwards, host of “The Political Cesspool,” a white nationalist radio show based in Memphis and a director of two supremacist groups, the Council of Conservative Citizens and the American Freedom Party. (Interlocking directorships are common in the movement.) “But we’re not going to step back from the truth.”

As much as supremacist groups have criticized the Charleston shootings, they have benefited from their moment in the news. At Stormfront.org, daily traffic has more than doubled since the shootings. The site has had 3.1 million visits in the past 90 days, according to Google Analytics.

Edwards, who is 34 and calls himself a “paleo-conservative,” listed grievances such as those Roof spelled out — a litany of troubles blamed on blacks and Jews and a frustration that the country seems to celebrate ethnicity, race and sexuality for everyone except straight whites.

On his radio show three days after the shootings, Edwards declared that the real problem is “violence perpetrated by black males. Violence from white males — it’s a once-in-a-blue-moon occurrence.” His show came out of a commercial break with a snippet of music, the Four Seasons singing, “Let’s hang on to what we’ve got.”

After the shootings, supremacist leaders were quick to post statements condemning violence, but although they’re careful about their language, some of them say further attacks are inevitable.

“Frankly, this movement is in such disarray,” said Johnson, the 61-year-old American Freedom Party chairman, who traces his involvement to his support of George Wallace’s 1972 presidential bid. “You cannot expect there to be no retaliation by certain disaffected portions of white society when you have crime after crime by blacks against whites. People are going to rebel, and that’s what this young man did.”

Violent crime across the country has dropped to near-record lows over the past two decades; the national crime rate is about half of what it was at its peak in 1991, according to the government’s Bureau of Justice Statistics. Despite that, polls repeatedly indicate that Americans perceive crime to be on the increase.

Some supremacist groups have become more subtle about their language, seeking “to recast white nationalism as nonviolent and as less hateful,” said Berger, the Brookings researcher. “Many white nationalists realize they are losing the generational battle for the hearts and minds of young people.”

Stormfront’s site asks followers to “avoid racial slurs in comments/communications. Many of us love to use them but they tend to trigger what I call the ‘Ignore Feature’ that has been programmed into the minds of so many. . . . You should strive to appear ‘normal.’ ”

If other lone wolves are lurking among those who lace supremacists’ comment boards with diatribes against blacks and Jews, finding them before they turn violent is harder than ever, investigators and white nationalist leaders agree. In most cases, extremists who turn to violence do so not because some group has pressed them into criminal service, but because of some precipitating trauma in their own lives — conflict with a parent or partner, a job loss, a personal slight.

“For every hate crime, there’s something that pushes him over the edge,” said Gomez, the former FBI agent.

The combination of online anonymity, a new caution about language and a new generation’s broader acceptance of a multi-racial society is making it harder than ever for investigators to determine which extremists “really believe that shooting nine people in a church is going to start a revolution,” Gomez said. “The sad truth is you have to wait for them to do something.”

On that, investigators and supremacists agree. “I don’t see how you can tell the crazy ones from the merely disaffected ones,” Johnson said, “because when you read their comments, they all sound exactly the same.”

Dan Morse in Charleston and Jeremy Borden in Columbia contributed to this report.