Flowers and a photo of killed police officer Keith Palmer on Whitehall near the Houses of Parliament in London, Thursday March 23, 2017. On Wednesday a knife-wielding man went on a deadly rampage, first driving a car into pedestrians then stabbing a police officer to death before being fatally shot by police within Parliament's grounds in London. (AP Photo/Kirsty Wigglesworth)
Flowers and a photo of killed police officer Keith Palmer on Whitehall near the Houses of Parliament in London, Thursday March 23, 2017. On Wednesday a knife-wielding man went on a deadly rampage, first driving a car into pedestrians then stabbing a police officer to death before being fatally shot by police within Parliament's grounds in London. (AP Photo/Kirsty Wigglesworth) Credit: Kirsty Wigglesworth

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 in London, saying he had a long criminal record and once was investigated for extremism — but was not currently on a terrorism watch list.

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 (the policeman) around 10 stabs in the back,” 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. The 75-year-old victim was not identified.

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 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.

But 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.

Many suspects in British terrorist attacks and plots have had roots in Birmingham, and several local mosques have been linked to extremist clerics.

A home raided in Birmingham was one where Masood lived until late last year, a neighbor said. Shown a photo of him, Iwona Romek said “that is 100 percent” the man who lived next door to her for about five months.

Romek said he had a wife and child about 6 years old who he would walk to school. He rarely left home in the evening.

“He seemed like a normal family man who liked to take care of his garden,” she said. But one day she saw him packing their belongings in a black van and they were gone.

As police investigated, Parliament got back to business, opening with a minute’s silence for the victims. May saluted the heroism of police and the bravery of ordinary Londoners.

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.”