LONDON — A white supremacist and Nazi memorabilia collector was found guilty Wednesday of murdering a British lawmaker during the country's bitter Brexit campaign in what prosecutors called an act of "terrorism."

Jo Cox was killed in June. JO COX / AFP - Getty Images

Thomas Mair, 53, was convicted of killing pro-European Union "Remain" campaigner Jo Cox in broad daylight in front of shocked bystanders a week before June's national referendum.

The mother-of-two was stabbed 15 times and received three gunshot wounds in the attack outside her constituency office in the town of Birstall in West Yorkshire, northern England.

Cox was a high-profile supporter of the campaign to stay in the EU — and to keep the debate from being hijacked by immigration.

Shortly before her death, she wrote in her local newspaper that "it's fine to be concerned" about immigration, as "many people are."

"His premeditated crimes were nothing less than acts of terrorism designed to advance his twisted ideology"

Witnesses said Mair repeatedly shouted "Britain first" during the attack, the trial heard.

A pathologist testified the 41-year-old Cox attempted to shield herself during the attack by holding her hand to her face but the bullets passed through them and into her skull, ITV News reported.

Mair was also accused of wounding a 77-year-old bystander who desperately tried to intervene but was also stabbed.

He denied all charges but opted not to give evidence in his defense at the Old Bailey in London.

Thomas Mair in a custody photo taken after his arrest in connection with the murder of British lawmaker Jo Cox. West Yorkshire Police / AFP - Getty Images

The Southern Poverty Law Center, which tracks hate groups, said in June that Mair attended a meeting of white supremacists in London in May 2000. One of those present told the SPLC that Mair was a Holocaust denier and an admirer of the white power band, Skrewdriver.

The trial heard that, in the months before Cox’s killing, Mair repeatedly visited neo-Nazi, right-wing and white supremacy websites and carried out searches relating to the Ku Klux Klan using computers at local public libraries.

Detectives found a gold Third Reich Eagle ornament with a swastika on it on Mair’s bookshelf, ITV News reported.

A search of his home found books on German military history and the Holocaust including one entitled "March of the Titans: A History of the White Race."

Police also recovered press cuttings about Norwegian mass killer Anders Breivik, a printout of a Wikipedia entry on the White Patriot Party and information on a notorious South African neo-Nazi organization.

At the first court hearing in the hours following his arrest, Mair gave his name as "death to traitors, freedom for Britain."

Sue Hemming, head of counter-terrorism at England’s Crown Prosecution Service said in a statement Wednesday that Mair had “offered no explanation for his actions” but that “his premeditated crimes were nothing less than acts of terrorism designed to advance his twisted ideology.”

She added that prosecutors would “continue to … combat those who seek to sow hatred and division by advancing extremist ideologies.”

Attack witness Clarke Rothwell told the trial that Mair shouted words like "this is for Britain" and "put Britain first" before reloading his gun and shooting for a third time.

Yes, Thomas Mair is a Neo-nazi and white supremacist. He's also a terrorist. Just like the killers of Lee Rigby, just like the 7/7 bombers — Rohit Kachroo (@RohitKachrooITV) November 23, 2016

Tracy Bywood, who was in a nursing home kitchen overlooking the scene, said the Labour Party lawmaker "went down on the floor like a sack of potatoes.”

"It was so awful to see a woman have such animosity shown towards her," the witness added.

Cox was a Cambridge University graduate who worked for global charity Oxfam, where she handled international humanitarian campaigns, before being elected to the House of Commons in 2015.

Secretary of State John Kerry said in June that her killing was "an assault on everyone who cares about and has faith in democracy."

Mr Justice Wilkie: The death of #JoCox was both a personal tragedy and one of great political significance @itvcalendar — Katie Oscroft (@katieoscroftitv) November 23, 2016