BIRSTALL, England — The man detained by police in connection with the killing of a rising star of British politics had long-standing ties to a U.S.-based neo-Nazi organization and, in the past, had ordered a how-to guide for assembling a homemade gun, according to a watchdog group that tracks extremist behavior.
The details emerged as police on Friday tried to piece together the motive behind the killing of the British lawmaker, Jo Cox, who was stabbed and shot at midday Thursday in an attack that stunned the nation and led to a suspension of Britain’s European Union referendum campaign just a week before the vote.
Larger questions over security and threat levels were also underscored. Police said another man was arrested in March for sending abusive messages to Cox, who had been a strong advocate of an inclusive and multicultural Britain amid a wave of hostility toward immigrants that is helping to fuel the anti-E.U. campaign.
On Friday, British Prime Minister David Cameron and the Labour Party leader, Jeremy Corbyn, made a joint visit to a makeshift memorial set up near the site of Cox’s slaying in Birstall, a town near the city of Leeds.
“Today our nation is rightly shocked,” he said. Corbyn called Cox’s murder “an attack on democracy.”
People who knew her — and those who didn’t — placed flowers at the foot of a statue in Birstall’s central square. Also left in tribute: heartfelt letters, poems and cards expressing sorrow and disbelief.
The visitors reflected the diversity of the community. White Britons, Eastern European immigrants and members of the area’s longstanding South Asian community all gathered to pay respects.
“She was genuine, caring. A proper Yorkshire lass. She wasn’t one of those politicians who just tries to make her name. She genuinely worked hard for the community,” said Nazir Daud, 41.
Daud said Cox never failed to return his calls or text messages relaying concerns among worshippers at his mosque. He scrolled through a stream of text exchanges find the last: a message from Cox wishing him a happy Ramadan.
“She stood for a multicultural vision of Britain,” he said.
Cox’s suspected killer was not named by police, but he was identified in the British media as 52-year-old Tommy Mair, a local resident whom neighbors described as quiet and devoted to his mother. Family members said that Mair had never expressed strong political views, but that he had an obsessive personality. He was arrested shortly after the attack.
According to documents obtained by the Southern Poverty Law Center, the U.S.-based organization that tracks extremist groups, Mair was a longtime supporter of the National Alliance, a once-prominent white supremacist group. In 1999, Mair bought a manual from the organization that included instructions on how to build a pistol, the center said.
Cox was shot by a weapon that witnesses described as either homemade or antique.
In all, Mair sent $620 to the group’s publishing arm for titles including “Incendiaries,” “Chemistry of Powder and Explosives,” “Improvised Munitions Handbook” and “Ich Kampfe,” published by the World War II-era Nazi party, the law center said.
The Daily Telegraph also reported that Mair had subscribed to a South African magazine published by the White Rhino Club, a pro-apartheid group.
Officials have not commented on a possible motive for the killing. But British media organizations including the Guardian, the BBC and Sky News quoted witnesses as saying that the assailant shouted “Britain first!” during and after the attack.
Britain First is the name of a far-right group that stages provocative anti-Muslim demonstrations. After Thursday’s attack, the organization posted a statement on its website denying involvement and saying it “would never encourage behavior of this sort.”
Nick Lowles, chief executive of the British-based anti-extremist group Hope Not Hate, said Mair had affiliation with far-right groups that stretched back decades, although he was not a prominent player in any of them.
It remains unclear whether the attack had any links to debates over immigration ahead of the E.U. vote next Thursday, Lowles said. But he described the current atmosphere as “increasingly toxic.”
“That leads to increased prejudice. That leads to increased hate. And, at some stage, that leads to violence,” he said. “Whatever the outcome next week, the U.K. has become a much more intolerant and divided society. It’s going to take a long time to heal.”
When German Chancellor Angela Merkel was asked about the Cox, she called on British politicians to moderate the rhetoric in their campaigning. “Exaggerations and radicalization of part of the language do not help to foster an atmosphere of respect,” she said.
Anna Turley, a Labour lawmaker, told the BBC that she and Cox talked often about the “increasing nature of hostility and aggression, particularly towards female MPs, particularly on social media.” Turley added: “We were all reviewing our security.”
But she insisted that “Jo would not have wanted us to be hidden and be behind walls.”
Flags flew at half staff outside 10 Downing Street and Buckingham Palace.
The killing was of the sort that has become all too common in the United States, but is virtually unheard of in Britain: without warning, hyper-violent and ultimately, perhaps, inexplicable. Parliament urged lawmakers to review their personal security measures.
Witnesses told British media that the assailant appeared to have been waiting for Cox outside a library in Birstall where she had been meeting constituents as part of her usual weekly schedule.
Witnesses recounted a savage attack in which the assailant targeted Cox with a gun as well as with a knife. The attacker continued to stab and kick Cox even after she had fallen to the ground, bleeding.
The killing shook Britain to the core and prompted an outpouring of grief across the political spectrum. Both the pro- and anti-E.U. camps announced that they were suspending their campaigns at least until the weekend. Cox, 41, was a supporter of keeping Britain in the 28-nation bloc, and was a champion for humanitarian efforts including greater aid for Syrian refugees.
“We’ve lost a great star,” Cameron told the BBC.
Some commentators took note of the anti-immigrant, anti-politician sentiments that have been further whipped up during the divisive E.U. referendum campaign.
On the same day as the shooting, Nigel Farage, the leader of the anti-immigrant U.K. Independence Party, unveiled a referendum campaign poster showing a massive queue of migrants with the slogan: “Breaking Point. We must break free from the E.U. and take control of our borders.” Nicola Sturgeon, the first minister of Scotland, called it “disgusting.”
“When you shout ‘breaking point’ over and over again, you don’t get to be surprised when someone breaks,” said the Spectator magazine’s Alex Massie. “When you present politics as a matter of life and death, as a question of national survival, don’t be surprised if someone takes you at your word. You didn’t make them do it, no, but you didn’t do much to stop it either.”
The Quilliam Foundation, a London-based counter-extremism think tank, said that it was “looking increasingly likely that this was an act of nationalist far-right terrorism.”
Gun attacks in Britain are rare, a fact that authorities here attribute to extremely tight gun-control restrictions. Attacks against members of Parliament are also highly unusual, and beyond those at the highest reaches of government, politicians customarily do not have security details.
The last British lawmaker to be killed while in office was Conservative Ian Gow in 1990 from a bomb placed under his car by the Irish Republican Army. The same year, a former Parliament member, Donald Kaberry, was wounded in an IRA bombing and died the next year.
The attack on Cox echoed the 2011 shooting of then-Rep. Gabrielle Giffords (D-Ariz.) in Tucson, also while meeting constituents. Giffords was severely wounded but survived. On Thursday, she tweeted: “Absolutely sickened to hear of the assassination of Jo Cox. She was young, courageous, and hardworking. A rising star, mother, and wife.”
Cox, the mother of two young children, was elected in May 2015. She also was national chair of Labour Women’s Network. On her Twitter page, she described herself as “mum, proud Yorkshire lass, boat dweller, mountain climber and former aid worker.” She previously worked as an adviser to the Britain-based aid group Oxfam.
Nick Grono, head of the Freedom Fund, an anti-slavery group where Cox once worked, said she “lived her ideals.” She and her husband would spend Christmas vacations in the Balkans, working with children who had been traumatized by the conflict there, he said. He also said she enjoyed “hiking everywhere around Scotland.”
In Parliament, Cox had been outspoken about the need to do more to protect civilians in Syria, and had argued in the House of Commons for Britain to accept 3,000 child refugees.
Before Cox’s death was announced Thursday afternoon, her husband posted a photo of her on Twitter standing beside their houseboat in London.
“Jo believed in a better world and she fought for it every day of her life with an energy, and a zest for life that would exhaust most people,” wrote Brendan Cox. “She would have wanted two things above all else to happen now, one that our precious children are bathed in love and two, that we all unite to fight against the hatred that killed her. Hate doesn’t have a creed, race or religion, it is poisonous.”
Adam reported from London.