Neighbours say suspect, named locally as Thomas Mair, would help them with gardening and did voluntary work

Jo Cox is believed to have been shot dead by one of her own constituents, a jobbing gardener little known beyond the Yorkshire estate on which he lived.

Politicians express shock over killing of MP Jo Cox Read more

Police are investigating claims that the suspect, named locally as Thomas Mair, 52, had dangerous political affiliations, following witness accounts that he shouted “Britain first” as he launched the fatal assault on Thursday afternoon.

The picture that emerged of the man known as Tom or Tommy from those who knew him best was of a quiet and caring loner. His half brother, who is mixed race, claimed he had been volunteering at a school for children with disabilities for several years and had never expressed any racist views. Duane St Louis, 41, described his brother as a devoted son who shopped for their mother twice a week and who had visited her on Wednesday night to help tune her TV.

Mair grew up not with his mother, Mary, but his maternal grandmother, Helen, who died in 1996. The pair lived in a semi-detached house on the Fieldhead estate in Birstall, 15 minutes walk up the hill from where Cox was killed. St Louis said his brother lived alone after their grandmother’s death and had never married or had children. He had not had a girlfriend for years. “He had one girlfriend when he was younger but his mate took her off him and he said he didn’t want another one,” said St Louis.

Despite Mair living in the same house for at least 40 years, his neighbours told the Guardian they knew little about him.

They said he was quiet and polite, volunteering to do their gardens and offering horticultural tips as he passed down Lowood Lane on his regular strolls into Birstall to use the computers at the library.

It is believed he had mental health problems and was quoted as praising a particular passage of care he had undertaken in the past.

In 2011, he was photographed by the local paper volunteering in nearby Oakwell Hall country park. The previous year he was quoted in the Huddersfield Daily Examiner, saying he had begun volunteering after attending Pathways Day Centre for adults with mental health problems.

“I can honestly say it has done me more good than all the psychotherapy and medication in the world,” he said. “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.

“When you have finished there is a feeling of achievement which is emotionally rewarding and psychologically fulfilling. For people for whom full-time, paid employment is not possible for a variety of reasons, voluntary work offers a socially positive and therapeutic alternative.”

Facebook Twitter Pinterest Flowers are laid at a statue to Joseph Priestly in Birstall near to the scene where Labour MP Jo Cox was shot. Photograph: Oli Scarff/AFP/Getty Images

Talking outside his house in Dewsbury on Thursday, St Louis said he couldn’t believe the news. “I was watching Sky News and I recognised him in handcuffs on the ground,” he said. “It felt like a dream. I just couldn’t believe he’d do something like that.

“I phoned my mum and she was watching too. She tried to phone his mobile but couldn’t get through and she knew something was up.”

He insisted his brother had never expressed any racist views and seemed fine to have a mixed-race sibling. Asked whether he had any strong political views, St Louis said: “Not that I know of.” He said he had no idea how Mair had got hold of a gun and did not have any hobbies that would require a firearms licence.

The men have another brother, Scott Mair 49, who told reporters he had wept when he heard about the killing. He said: “I am 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.”

On the Fieldhead estate, neighbours said Mair appeared perfectly normal on Thursday. One mother and daughter said they had seen him stroll past their house at around 12.30pm, 25 minutes before Cox was shot and stabbed. “I looked out of the window at about 12.30 and he walked past carrying his bag, wearing a cap. He looked perfectly calm and normal,” said Emma John, 30. Her mother, Kathleen Cooke, said he did not seem particularly agitated.

Two separate witnesses have described the gunman in the attack as shouting “Britain first” as he stabbed, shot and kicked Cox.

Graeme Howard, 38, who lives in nearby Bond Street, said: “He was shouting ‘Britain first’ when he was doing it and being arrested.”

Another witness, Clarke Rothwell, told the Huddersfield Daily Examiner: “He was shouting what sounded like ‘Britain first, Britain first’ but then seemed to panic and hurried off. He seemed scared and hurried off towards Union Street, dumping a jacket on the floor. I got into my van and tried to follow him but I lost him.”

A name matching that of the alleged suspect appears on an extremist website. It describes him as “one of the earliest subscribers and supporters of” a certain extremist publication which is alleged to be linked to white supremacy.

The semi-detached house where it is believed the gunman lived was surrounded by a police cordon on Thursday afternoon. Uniformed officers guarded the property as the immaculate front garden was searched by forensic experts. Net curtains in the front room were drawn. Neighbours said they were just about to settle down to watch the England v Wales match when police arrived at the property.

Facebook Twitter Pinterest Jo Cox died after being shot and stabbed in her constituency town. Photograph: Yui Mok/PA

One woman, Karen, said Mair did her mother’s garden regularly until a few years ago. She thought he had lived alone for some years since his grandmother died.

Local teenagers said he was a quiet man who kept himself to himself unless they congregated on the wall behind his house, which he didn’t like. “He’d shout at us,” said a 17-year-old.

“All this we are hearing now is totally at odds with the man we thought we knew,” said one neighbour. “We knew him as someone who helped others, not hurt them.”

Nick Gannon, 33, who lived two doors away from Mair, has known him since he was 10 years old. “It’s shocking,” he said. “He were a quiet guy, you would not think it of him. He would cut elderly people’s grass voluntarily. There were no reason to think he would be capable of something like this.

“He was friendly. If you said hello to him, he would say hello back. He was not aggressive or anything. He wasn’t frightening.”

He added that Mair’s grandmother had died about 20 years ago and he had lived alone ever since.

Mair’s mother, Mary, said she was too upset to speak on Thursday, but her neighbours talked of their shock at the news. One woman, who asked not to be named, said Mair was a “devoted son” who did his mum’s shopping twice a week, and would bring two carrier bags around on foot, before walking several miles up the hill back to his house. He had visited last on Wednesday, she said.

She insisted it was “totally out of character” and that he had never been in trouble with police before. She said he “practically lived in the library” and liked to write his own stories.

“He was obsessed with books,” she said. “His house is full of them.”