West Yorkshire Police arrested a man on Friday in connection with the murder of British Labour Party MP Jo Cox, who was shot and stabbed in Birstall, Northern England, on Thursday. The assailant, identified as 52-year-old Thomas Mair, will appear before the Westminster Magistrates' Court on Saturday, reported BBC.

While no motive has been established yet, reports claim that Mair was a supporter of the National Alliance, a neo-Nazi organisation in the United States. Investigators are now looking into his ties with such groups, reported CNN. Apart from murder charges, Mair is also accused of causing grievous bodily harm, possessing a firearm with intent to commit an offence and possessing an offensive weapon.

Mair’s brother Scott told The Daily Telegraph that he was “struggling to believe what has happened.” “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,” he said.

An avid campaigner for the rights of refugees, Cox, 41, was shot dead just a week before the crucial referendum on whether Britain should continue to be part of the European Union. The Labour Party MP was a vocal supporter of Britain remaining part of the bloc.

Labour Party leader Jeremy Corbyn said her death has left the country “in shock and grief”, and that she “died doing her public duty at the heart of our democracy, listening to and representing the people she was elected to serve”.