Police later announced the death of Cox, a campaigner for Britain to remain in the European Union. Officers said a 52-year-old man had been arrested and a firearm had been recovered from the scene. "This was a localised incident, albeit one which has a wider impact," West Yorkshire Police and Crime Commissioner Mark Burns-Williamson told reporters.
Cox, a former aid worker, was only elected to parliament last year but had already made her name campaigning for the government to do more to aid Syrian refugees and for Britain to stay in the EU. After the attack, the "Remain" camp said it was suspending all campaigning for Thursday and Friday while a spokesman for the rival "Vote Leave" group said their "battle bus" was returning to headquarters.
Prime Minister David Cameron cancelled a planned rally during a historic but controversial visit to Gibraltar as part of his campaign for Britain to remain in the EU in the June 23 vote. "We've lost a great star. She was a great, campaigning MP with huge compassion, with a big heart," Cameron said in televised remarks. On a visit to Copenhagen, US Secretary of State John Kerry said: "It is an assault on everybody who cares about and has faith in democracy," he added.
Her husband Brendan wrote: "Jo believed in a better world and she fought for it every day of her life." Over parliament the British flag flew at half-mast. The human rights campaign group Avaaz called for a vigil outside the Houses of Parliament and a church in Birstall also said it was planning a commemoration later on Thursday. Grieving local residents laid flowers to near the scene of the attack as police forensic officers were seen examining a shoe and a handbag in a cordoned-off area.
One witness, local cafe owner Clarke Rothwell, said that Cox had been shot three times. "He shot this lady once and then he shot her again, he fell to the floor, leant over shot her once more in the face area," he told the BBC. Sky News television quoted unconfirmed reports that the shooter shouted "Britain first". He was named by British media as local man Tommy Mair. The attack halted a frantic day of campaigning, as two new opinion polls indicated that more Britons now want to leave the EU than want to stay.
If they prove correct, Britain would become the first state in the nearly six-decade history of the bloc to leave. The looming prospect of a Brexit has sparked volatility in the financial markets and sent the pound plunging, and prompted interventions from a number of EU leaders. "I know it's very difficult for us to be optimistic today, we know the latest polls," EU President Donald Tusk said on a visit to Helsinki.