More details are emerging about the man who tore along the Westminster Bridge running down pedestrians and going on a stabbing spree outside Parliament on Wednesday, as British authorities carried out raids and made arrests on Thursday.

London police identified the suspected Islamist terrorist as Khalid Masood, a 52-year-old British man – though it has been reported that this is not his birth name.

The man is known for using many aliases.

A flat in the heart of the Olympic Village in East London belonging to a woman, identified as Rohey Hydara, was raided and searched by officers Thursday night.

She had lived with Masood in at least two separate addresses but it was unclear what kind of relationship they had.

Police detained eight people, but did not disclose the identities of the arrested or what connection they could have to the London attack.

Three people were killed in the attack, including an American man, a British woman of Spanish origin and a police officer outside the grounds of the Parliament. A fourth victim, a 75-year-old man, died Thursday night after his life support was withdrawn at King’s College Hospital.

Masood was fatally shot after stabbing to death the police officer.

Dozens were injured in the deadliest act of terror in the UK since 2005, when coordinated bombings by Islamist extremists on London’s public transportation system claimed 52 lives.

Police said Masood was not the subject of any current investigation and that “there was no prior intelligence about his intent to mount a terrorist attack.”

He had been arrested previously for assault, possession of offensive weapons and public order offenses.

His first conviction was in November 1983 for criminal damage and his last was in December 2003 for possession of a knife.

The attack was claimed by ISIL on Thursday. 

UK’s Prime Minister Theresa May declared that “we are not afraid.”

In a speech to Parliament on Thursday, May said the perpetrator had been investigated years earlier over extremist concerns but that authorities viewed him as a “peripheral figure.”

The European Union Security Commissioner Julian King suggested that there could be a link between Wednesday's attack in London and the suicide bombings in Brussels which took place the same day a year ago and left 32 people dead.

"I don't think it was a complete accident that this attack took place on the first anniversary of the Brussels attacks," King said.

He did not say whether the link went beyond that both took place on March 22.

King added that "the terrorist threat remains extremely high across Europe."

On a visit to the United Nations in New York, Britain’s Foreign Secretary Boris Johnson said on Thursday that Londoners were "attacked in a cowardly and a despicable way" by Masood and noted how the multiple nationalities of the victims showed how "an attack on London is an attack on the world".

Meanwhile, a spokesperson for a car rental company, Enterprise Holdings, confirmed that the car used in the attack belonged to them.

"An employee identified the vehicle after seeing the license plate in an image online. We ran another check to verify, and immediately contacted the authorities."

The Westminster Bridge has reopened to traffic less than 24 hours after the attack.‍