Jo Cox, a British member of parliament from the Labour Party, died Thursday after being shot and stabbed that morning. The politician had been campaigning for the Remain camp ahead of next week's referendum in Britain on whether the country should leave the European Union.

Local media reports suggest Cox's assailant was a 52-year-old man who shouted "Britain First!" -- a slogan identified with the sort of far-right, anti-immigration politics that animates some who want Britain to break away from the E.U., a so-called Brexit.

As my colleagues Griff Witte and Karla Adam report, Cox's murder has led to an outpouring of grief from across the British political spectrum. Both the pro- and anti-E.U. camps suspended their campaigns after news of the attack broke.

Cox, 41, had been elected to parliament last year. Before politics, she had been a humanitarian campaigner and aid worker for a decade; she met her husband Brendan, a former official with Save of the Children, while working in the field. Brendan Cox became an adviser on international development in an earlier Labour-led government. Jo Cox was seen as a rising star in the center-left party.

"Jo cared about everybody, but she reserved a special place in her heart for the most vulnerable and the poorest citizens of the world," Sarah Brown, wife of former British Prime minister Gordon Brown, said in a statement. "She was fearless, she was endlessly upbeat and she reached out to so many to join her cause. Her mission was to make the world a better place."

United Kingdom pays tribute to slain British lawmaker Jo Cox

GLASGOW, SCOTLAND - JUNE 17: Candles surround a photo of Labour MP Jo Cox before a vigil in her memory as the Leader of Scottish Labour party Kezia Dugdale holds a rose in George Square on June 17, 2016 in Glasgow, Scotland. The Labour MP for Batley and Spen was about to hold her weekly constituency surgery in Birstall Library yesterday when she was shot and stabbed in the street on June 16. A 52-year old man is being held in Police custody in connection with the death. (Jeff J Mitchell/Getty Images)

In particular, Cox championed the plight of Syrian refugees, even as other politicians in Britain and Europe sought to raise the drawbridge on hundreds of thousands of people fleeing conflict. In April, she spoke in defense of a bill to accept 3,000 child refugees, which was voted down by Conservatives in parliament. Here's a portion of her address, as transcribed by Buzzfeed UK:

We all know that the vast majority of the terrified, friendless and profoundly vulnerable child refugees scattered across Europe tonight came from Syria. We also know that, as that conflict enters its sixth barbaric year, desperate Syrian families are being forced to make an impossible decision: stay and face starvation, rape, persecution and death, or make a perilous journey to find sanctuary elsewhere.
Who can blame desperate parents for wanting to escape the horror that their families are experiencing? Children are being killed on their way to school, children as young as seven are being forcefully recruited to the frontline and one in three children have grown up knowing nothing but fear and war. Those children have been exposed to things no child should ever witness, and I know I would risk life and limb to get my two precious babies out of that hellhole.​
I am deeply proud of the government for leading the way internationally on providing humanitarian support to Syrian civilians. Their commitment in terms of finances and policy to help people in the region, and across the middle east and north Africa, will save lives. However, in the chaos caused by the Syrian conflict and many other conflicts, many thousands of already deeply scarred children have become separated from their parents and carers, and they are already in Europe. The government’s generosity to date has not extended to those vulnerable children.
We know that identifying the exact number of unaccompanied minors is difficult, but the latest estimates suggest that there could be up to 95,000 such children in Europe tonight—four times the number we thought. That means that, if we decide tonight to take 3,000 of them, that will be just 3% of the total. That is our continent’s challenge, and we must rise to it.

Last October, Cox co-authored an op-ed in the Guardian with a conservative politician, calling on Britain to invest more in efforts to provide for refugees and to work toward improving Europe's "collective response" to the humanitarian crisis spilling out of the Middle East.

"Syria is our generation's test, our responsibility," the politicians wrote. Cox established a parliamentary working group on Syria and organized debates on refugees.

Cox also opposed the anti-immigration politics that has come to define a section of Britain's right wing. In her maiden speech in the House of Commons, she celebrated how immigration had "deeply enhanced" her constituency near the northern English city of Leeds.

"Our communities have been deeply enhanced by immigration, be it of Irish Catholics across the constituency or of Muslims from Gujarat in India or from Pakistan, principally from Kashmir," she said, "While we celebrate our diversity, what surprises me time and time again as I travel around the constituency is that we are far more united and have far more in common with each other than things that divide us."

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