Investigators searched for answers after a man fatally shot British politician Jo Cox in her district in northern England — a stunning attack in a nation with tight gun laws.
Cox, a parliament member, was attacked in Birstall on Thursday after a meeting with constituents, the Press Association news service reported.
The 41-year-old mother of two died a few hours later at a hospital. Her death comes a week before a crucial vote on whether the UK should stay in the European Union.
Man in custody
Police detained Tommy Mair, 52, for questioning after the shooting, according to the Press Association.
Weapons, including a firearm, were recovered at the scene, said Dee Collins of West Yorkshire Police.
Authorities have not commented on the circumstances surrounding the attack and a motive wasn't immediately clear.
After the attack, the UK Met Police said it arrested a man in connection with "malicious communications" sent to Cox in March.
"The man subsequently accepted a police caution," police said.
The man in custody for questioning is not the same one investigated in the March incident, police said.
'Put Britain first'
In a nation with such controlled gun laws and low homicides linked to weapons, Cox's attack was especially jarring.
Witness Clarke Rothwell, who runs a cafe near the crime scene, told the Press Association the gunman yelled something before he shot Cox three times.
"He was shouting 'Put Britain first.' He shouted it about two or three times. He said it before he shot her and after he shot her," Rothwell said.
Attacks against British politicians are so rare, lawmakers at her level are mostly unaccompanied by a security detail.
Passionate campaign
The killing comes amid a heated campaign leading up to a June 23 referendum on the UK's membership in the European Union.
Parliament members have been subjected to public ire, and accused of lying and making up arguments on both sides of the debate.
Lawmakers temporarily halted official campaigning following the attack, putting the passionate debate on the back burner a week before the vote.
"It's right that all campaigning has been stopped after the terrible attack on Jo Cox," Prime Minister David Cameron tweeted Thursday.
Cox was in favor of keeping the UK in the European Union. She championed for the rights of immigrants, saying leaving the EU would not reduce the number of refugees coming to the UK.
Supporters calling for an exit from the EU have cited the high number of immigrants as one of the reasons, with tensions high on both sides of the debate.
In one of Cox's last posts on social media, she said while immigration "is a legitimate concern," it's not a good reason for the UK to leave the EU.
Fellow Labour MP Mike Gapes described her as a rising star in the party.
"She's had a big impact already," he said. "She's been one of the most outspoken people calling for more to be done to stop barrel bombing in Syria and to get humanitarian corridors to help for the refugees from Syria."
Britain First, a fringe nationalist political party that wants the nation to leave the European Union, denied any connection to the attack following reports of the assailant's comments.
In a statement, it said the party "would never encourage behavior of this sort."
Witness: Attacker kicked Cox
Witness Hichem Ben Abdallah said the attacker kicked Cox as she lay on the ground. A bystander intervened and the attacker produced a gun and shot her, Abdallah told the Press Association.
"There was a guy who was being very brave and another guy with a white baseball cap who he was trying to control and the man in the baseball cap suddenly pulled a gun from his bag," Abdallah said.
"The gun went off twice," Abdallah told the Press Association. "I came and saw her bleeding on the floor."
Police said no one else is being sought in relation to the attack.
Authorities search home
Police cordoned off Mair's house in Birstall and searched it Thursday.
A neighbor who did not want to be identified said police questioned her and asked if she knew Mair.
She said he seemed to like gardening and also tended to other neighbors' gardens.
Mair lives alone and had lived in the house a long time, she said. She didn't believe he had a regular job and she said she would see him around at odd hours
Husband: Death starts 'painful' chapter
The MP's husband, Brendan Cox, said her killing marked the "beginning of a new chapter in our lives."
"More difficult, more painful, less joyful, less full of love," he said.
"I and Jo's friends and family are going to work every moment of our lives to love and nurture our kids and to fight against the hate that killed Jo."
Slain MP's husband: 'Jo would have no regrets about her life'
Crowds gathered for vigils in Birstall and in London's Parliament Square to pay tribute to the slain politician.
Tributes pour in
London Mayor Sadiq Khan said Cox "made more impact than others make in a whole parliamentary career" during her year in parliament.
"Everyone who met Jo knew she was special. I knew her from her time as a fearless campaigner working on behalf of some of the world's poorest and most marginalized people," he wrote.
Democratic presidential candidate Hillary Clinton paid tribute to Cox.
"This is how we must honor Jo Cox — by rejecting bigotry in all its forms, and instead embracing, as she always did, everything that binds us together," she said in a statement.
The attack bore some similarities to the 2011 shooting of a U.S. congresswoman Gabby Giffords.
Giffords, then 40, was shot in the head at a constituent event outside an Arizona grocery store.
While she survived and spent months recovering in hospital, six people were killed. She resigned a year later to focus on her health and continues to struggle with the effects of the shooting.
The attack resonated with Giffords, who said she was "absolutely sickened" by it.
"Just like January 8, 2011, did not deter America from its founding ideals, the British principle of pluralism and the nation's democratic institutions will endure," she said in a statement.