CARDIFF, Wales — He was born in Singapore, but his family moved back to Britain when he was a child. He had marital problems, and was known by locals at the pub as belligerent and aggressive. He had Muslim neighbors, who described his behavior as unremarkable, and his children had Muslim friends.
No one here on the cul-de-sac where Darren Osborne, who is in his late 40s, lived in an outer district of the Welsh capital, Cardiff, could readily explain what he is believed to have done: Rent a van, drive it 150 miles to London, and plow into a crowd of Muslims leaving Ramadan prayers at the Finsbury Park Mosque early Monday.
The authorities have not formally charged Mr. Osborne; he was identified by British news organizations on Monday, including the BBC. The police raided his house here on Monday, and officers have been posted outside.
The authorities have said that the suspect in Monday’s attack was arrested on suspicion of the commission, preparation or instigation of terrorism including murder and attempted murder.
The assault injured several others; seven people remain in hospitals with a range of injuries. One man died at the scene, but the cause was unclear. Mr. Osborne was pinned down by bystanders and was shielded by an imam and other men before being hauled away by the police.
Prime Minister Theresa May of Britain called the act a terrorist attack targeting Muslims, and it was widely seen as yet another assault on the cosmopolitan, multicultural British capital, which had already endured two terrorist assaults since March. It also raised questions about where the line between terrorism and hate crimes can be drawn, and whether the distinction is even meaningful, particularly in cases of severely disturbed individuals.
But for residents here on Glyn Rhosyn, the terraced street where Mr. Osborne lived in a semidetached two-story house with a front garden that stood out among its neighbors for its lack of tidiness, the immediate reactions were shock and sadness.
“My husband and I called him the ‘mad man,’ ” said Jennifer Mears, who lived a few houses away from Mr. Osborne and who has resided in the area for more than 30 years. “He would always zoom up and down the road in various cars that he would bring here. I think he bought and sold lots of cars and it was annoying that he would park them all down the street.”
Many residents on the cul-de-sac said that Mr. Osborne had generally been polite when greeting them on the street, but that in recent weeks, he had appeared to be more aggressive. One neighbor described an episode when Mr. Osborne had shouted at his family and thrown things around his garden.
“He threw a plastic swing and it went over the fence and almost hit his neighbor,” said the resident, Laura Granger, who witnessed the episode. “When they complained about it, he swore at them and then went inside and started shouting at his children.”
She added: “We heard him scream at his wife, and he said, ‘Don’t make me get the cricket bat.’ ”
Mr. Osborne grew up in Weston-super-Mare, England, and moved to Wales a number of years ago.
Security Minister Ben Wallace said the suspect in the attack on Monday was “not known to the authorities in the space of extremism or far-right extremism,” and was believed to have acted alone. Investigators are only just starting to learn the full extent of the suspect’s beliefs and affiliations, however.
Locals at the nearby Hollybush pub said Mr. Osborne got drunk on Saturday night and became increasingly rowdy as the night went on, cursing at a group of younger men who were drinking in the corner.
Mr. Osborne’s children attend the local Glyncoed Primary School and have several Muslim friends, according to other parents in the area.
Amir Jark, a Muslim father of two children who attend the school, said that he had seen Mr. Osborne many times and that he had appeared to be kind and even loving toward children.
“I heard that he got into a fight with one of the parents in the playground last week, but I don’t think he’s shown hostility towards the Muslims here,” Mr. Jark said, before his 8-year-old daughter interrupted and said, “I don’t like him. He’s mean.”