LONDON — Authorities on Thursday identified a 52-year-old Briton as the man who mowed down pedestrians and stabbed a policeman to death outside Parliament, saying he had a long criminal record and once was investigated for extremism — but was not currently on a terrorism watch list.
As millions of Londoners returned to work a day after a rampage that killed four victims and injured at least 30, British Prime Minister Theresa May had a message for other attackers: "We are not afraid."
"Today we meet as normal — as generations have done before us, and as future generations will continue to do," she said to lawmakers' cheers in the House of Commons.
The Islamic State group claimed responsibility for Wednesday's attack, which police said was carried out by Khalid Masood, a U.K.-born resident of the West Midlands in central England. Masood plowed a rented SUV into pedestrians on London's Westminster Bridge, killing an American man and a British woman and injuring more than 30 people of almost a dozen nationalities. He then fatally stabbed a policeman inside the gates of Parliament before being shot to death by an officer.
A 75-year-old victim on the bridge died late Thursday of his wounds, police said.
Vincenzo Mangiacarpe, an Italian boxer visiting Parliament, said he saw the attacker get out of the car wielding two knives.
"You can imagine if someone was playing a drum on your back with two knives — he gave him around 10 stabs in the back, then he left the policeman and he came toward us," Mangiacarpe said.
The dead were identified as Kurt Cochran, 54, of Utah and British school administrator Aysha Frade, 43 — both struck on the bridge — and 48-year-old Constable Keith Palmer, a 15-year veteran of the Metropolitan Police.
Police arrested eight people — three women and five men — on suspicion of preparing terrorist acts as authorities sought Masood's motive and possible support network. One arrest was in London, while the others were in the West Midlands city of Birmingham. Police said they were searching properties in Birmingham, London and Wales.
Masood's convictions between 1983 and 2003 included assault, weapons possession and public order offenses, London police said.
He "was not the subject of any current investigations and there was no prior intelligence about his intent to mount a terrorist attack," police added.
As police investigated, Parliament got back to business, opening the day with a minute's silence for the victims.
May set the tone in the House of Commons, saluting the heroism of police and the ordinary actions of everyone who went about their lives in the aftermath.
"As I speak, millions will be boarding trains and airplanes to travel to London and to see for themselves the greatest city on Earth," she said. "It is in these actions — millions of acts of normality — that we find the best response to terrorism. A response that denies our enemies their victory, that refuses to let them win."
In 1,000-year-old Westminster Hall, the oldest part of Parliament's buildings, politicians, journalists and parliamentary staff lined up to sign a book of condolences. One uniformed policeman wrote: "Keith, my friend, will miss you."
The rampage was the first deadly incident at Parliament since 1979, when Conservative lawmaker Airey Neave was killed in a car bombing by Irish militants.
Some parliamentarians said they were shaken by Wednesday's attack, and all were somber. But they also were determined.
"There is no such thing as 100 percent security," said Menzies Campbell, a member of the House of Lords. "We have to learn to live with that."
The attack echoed deadly vehicle rampages in Nice, France, and Berlin last year that were claimed by the Islamic State.
The Islamic State said through its Aamaq News Agency that the London attacker — whom it did not name — was "a soldier of the Islamic State" who "carried out the operation in response to calls for targeting citizens of the coalition" fighting IS in Syria and Iraq.
The Islamic State has been responsible for violence around the globe and has called for Western followers to carry out bloodshed in their own countries, although the group has also claimed events later found to have no clear links to it.
Police believe the attacker acted alone, May told lawmakers, with no reason to believe "imminent further attacks" are planned. Britain's threat level from terrorism stands at "severe," the second-highest on a five-point scale, meaning an attack is highly likely.
Years ago, Khalid was "investigated in relation to concerns about violent extremism," she said, but called him "a peripheral figure."
Home Secretary Amber Rudd denied there had been an intelligence failure because the attacker had been known to police.
"I think that would be absolutely the wrong judgment to make," Rudd told the BBC. "I'm confident that as we get more information ... that we will learn more and take comfort from the information that we have and the work that the intelligence services do."
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