He feared immigrants, kept a victims' list that included a famous black hip-hop artist, and allegedly stalked his targets with a gun.
The case carries echoes of Anders Behring Breivik _ a lone gunman unleashing xenophobic fury in a shocking explosion of violence. And although the shooter who terrified the Swedish city of Malmo last year was less lethal than the Norway killer, new revelations provide a daunting reminder of the current of ethnic enmity beneath the Nordic countries' placid and tolerant surface.
Sweden, Denmark and Norway have won world renown for efforts to build peaceful and egalitarian societies, with generous immigration programs enshrined in government policy. In Stockholm, where every subway car gets a name as if it were a child's toy, rush-hour becomes a multiethnic, multi-faith parade.
Norway, home to the Nobel peace prize, and Sweden have been proud lands of refuge to asylum seekers from conflict zones, taking in tens of thousands of Afghans and Iraqis in recent years, as well as Somalis and people fleeing the 1990s Balkan conflicts. Overt expressions of racism are a rarely breached taboo.
Yet in a region that prizes social harmony as one of its greatest values, there are roiling racial tensions that threaten to destabilize this carefully nurtured balance.
Far-right and anti-immigrant parties have made astonishing gains in Scandinavia in recent years. Last year, the far-right Sweden Democrats entered Parliament for the first time with 6 percent of the vote. Norway's once fringe Progress Party is now the nation's second biggest, grabbing 22.9 percent of the vote in 2009. Denmark's People's Party has nearly doubled its parliamentary presence since 1998, shooting from 13 seats to 25. Finland's True Finns this year stunned Europe by winning 41 seats, up from their previous 6.
As these parties gain popularity, their rhetoric has grown more virulent _ fueling fears that immigrant-bashing words could fire the imagination of extremists in a region that has been prone to lone outbursts of murderous rage.
Swedes in particular are painfully aware of this vulnerability to lone attackers, remembering the murders of Prime Minister Olof Palme and Foreign Minister Anna Lindh _ both killed in public in downtown Stockholm _ and John Ausonius, dubbed Laserman for the gunsight he used in serial shootings of immigrants in the 1990s.
Last year's Malmo shootings that killed one and wounded at least 10 follow in this line. The 39-year-old suspect, Peter Mangs, feared immigrants were taking over the country, his father was quoted as saying by local media, and _ like Breivik _ he reportedly spent considerable time surfing extremist websites.
On Tuesday, the newspaper Sydsvenskan reported the suspect may have been more methodical than suspected; his computer reportedly contained a list of names including Jason Diakite, one of Sweden's most popular hip-hop performers, who uses the stage name Timbuktu that honors his Malian roots.
Experts fear virulent far-right rhetoric could provide the trigger for a madman simply looking for an excuse to kill.
"Rhetoric may help provide focus of paranoia and aggression in vulnerable and predisposed individuals," Niklas Langstrom, director of the Center for Prevention of Violence at Sweden's renowned Karolinska Institute, said in an email response to questions.
In last year's election campaign, a member of the Sweden Democrats wrote in a blog: "Get immigrants on film, put a bullet between their eyes, lay them in a sack, put a stamp on it and send them home." The party got nearly 6 percent of the national vote and 20 seats in Parliament.
Denmark's People's Party, which props up the governing center-right coalition, frequently reveals an acid side, with party leader Pia Kjaersgaard once sneering at Swedish cities as "Scandinavian Beirut."
It's difficult to gauge what motivates Scandinavia's far-right. Conventional sociological wisdom suggests that economic troubles go hand-in-glove with racial enmity and extremist politics. But that connection is hard to make in the Nordics.
Norway, awash in oil revenues, has the world's fourth-highest per-capita purchasing power, and its neighbors Sweden, Denmark and Finland all rank in the world's top 25, according to the International Monetary Fund. The countries' capitals are perpetual fixtures on lists of the world's most livable cities and generous social-welfare programs give comfort to even the most marginalized residents.
Some experts say the ease of life in the Nordics may in fact be a reason for the far-right's attaction among the young.
"At a certain age, you see everything in black-and-white and such a message can be attractive," Lagerlof said. "It offers them something to struggle with."
How much these sentiments influence violence is difficult to quantify. Sweden's Brottsforebyggande Radet, the national crime-prevention agency, reports a 10 percent drop in xenophobia-motivated crimes between 2008 and 2011, and a more than 20-percent fall in violent hate crimes.
A similar decline in far-right activity was reported this year by Sweden's Expo Foundation, from nearly 1,950 actions such as demonstrations and leaflet distribution in 2008, to 1,469 last year. Yet in the same period, the number of white-supremacist websites soared by a third, said Expo reseaarcher Daniel Lagerlof.
Expo's Lagerlof said it was difficult to say how many far-right extremists Sweden had. One sign, he said, may be the estimated 700 demonstrators who turned up in the town of Salem last year for an annual demonstration commemorating the murder of a skinhead who had played drums in one of Sweden's notorious "White Power" bands.
In addition, he said, there appears to be a strong overlap between hard-right extremists and the more moderate xenophobe parties that gained an air of legitimacy by entering parliaments. Lagerlof said an Expo investigation had found about one-fifth of the members of the Sweden Democrats' youth wing had demonstrable connections to the extremist fringe.
Some of the more extreme Scandinavian groups have shown virulence since the Norway killings.
In the wake of the attacks, Michael Ellegaard of Denmark's Frit Danmark announced that his organization would continue weapons training so members could protect themselves against "housebreakers and Muslims," local media reported.