It has emerged British Labour MP Jo Cox was just days away from receiving extra security after being harassed in a stream of threatening messages in the past three months.
The 41-year-old married mother became the first MP to be murdered in 25 years - and the first ever female MP - when she was shot and stabbed to death in a Yorkshire street on Thursday.
Her alleged killer has been named as Tommy Mair, 52, a loner with a history of mental illness who lived on a nearby council estate.
Police are investigating whether the attack was related to the impending European Union referendum after witnesses claimed they heard Mair shout "put Britain first" and "Britain first". The latter is the name of a far-right group that supports Brexit.
The Telegraph reports the Scotland-born Mair was a former subscriber to a South African magazine called SA Patriot, which is published by a pro-apartheid outfit called the White Rhino Club.
Mrs Cox made a name for herself in parliament as a passionate and kind MP who campaigned for the government to accept more child refugees from Syria. The day before the murder, she had been with her family campaigning for the Remain campaign on a flotilla on the River Thames.
Her husband Brendan has this morning tweeted a touching tribute to his wife - a photo of her next to the family's beloved houseboat.
Over the past three months Mrs Cox had become the target of a hate mail campaign and was in the process of receiving additional security at her constituency office in Birstall, West Yorkshire as well as at her houseboat in London.
There is no known link between Mair and the man who allegedly sent the hate mail. West Yorkshire police said a motive for the attack had not yet been established.
Mrs Cox, a mother of children aged three and five, was shot twice before falling to the ground where she was allegedly kicked and stabbed repeatedly.
Witnesses said she was shot a third time in the face and that Mair was allegedly trying to reload his antique-style weapon when another man, aged 77, tackled him. The older man suffered minor injuries. Mair reportedly lunged at others who attempted to intervene and then walked away from the scene.
The area was placed under a police lockdown and Mair was arrested soon afterwards.
Mair's 49-year-old brother Scott told reporters he cried when he heard about the murder.
"I am struggling to believe what has happened," he said. "My brother is not violent and is not all that political. I don't even know who he votes for. He has a history of mental illness, but he has had help."
Visibly shaking, he added: "I cried when I heard. I am so sorry for her and her family."
In 2011, Mair spoke of how he had volunteered to work as a groundsman at the nearby Oakwell Hall County Park, which had helped ease his mental health problems.
"I can honestly say it has done me more good than all the psychotherapy and medication in the world," he told a newspaper.
"Many people who suffer from mental illness are socially isolated and disconnected from society, feelings of worthlessness are also common mainly caused by long-term unemployment.
"All these problems are alleviated by doing voluntary work. Getting out of the house and meeting new people is a good thing, but more important in my view is doing physically demanding and useful labour."
Mrs Cox's murder has shocked Westminster and campaigning was suspended in the referendum as tributes flowed in from across the political spectrum.
Her husband Brendan, 37, tweeted a photograph of his wife two hours after she died and released a statement in which he urged people to "fight against the hatred that killed her". 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."
Buckingham Palace said that the Queen would write privately to Mr Cox. David Cameron paid tribute to a "committed and caring MP" and Jeremy Corbyn, the Labour leader, lauded a "much-loved colleague".
Mrs Cox nominated Mr Corbyn for the Labour Party leadership last year, shortly after becoming an MP following a career as a policy chief at Oxfam, but later said that she regretted it. Mr Corbyn added: "Jo died doing her public duty at the heart of our democracy, listening to and representing the people she was elected to serve."
Shopkeepers and passers-by on Market Street, Birstall, described the brutality of the attack. Clarke Rothwell, 42, a gas fitter, said that the suspect used an "old-fashioned gun" to shoot Mrs Cox before attacking her with a long "hunting knife".
Hichem Ben-Abdallah, 56, owner of a nearby restaurant, rushed to the scene. He said: "I saw a river of people rushing down the hill. They were screaming. A lady was down on the floor. The man pulled a gun - it was a makeshift gun. After the second shot I turned and ran. He walked away very calmly, down the steps."
Mrs Cox is the only woman to have been murdered while serving as an MP and the first since 1990, when Ian Gow was killed by an IRA bomb. MPs have expressed concerns about security at local surgeries since Stephen Timms, Labour MP for East Ham, was attacked by an Islamic fanatic in 2010.
Last night it emerged that a 37-year-old man was arrested after a death threat was made to the former Labour minister Ben Bradshaw. It followed an alleged campaign of extreme right-wing racist and homophobic abuse aimed at Mr Bradshaw and his staff in Exeter.
Police had cautioned a man in relation to a barrage of messages sent to Mrs Cox. The politician is said to have "thought little of them" until the "volume and frequency stepped up".