London Attacker Khaled Masood was known to British Security Services

Deputy Assistant Commissioner Neil Basu said it may never be possible to fully determine the motives of attacker Khalid Masood, who was shot dead Wednesday after running over pedestrians with an SUV and fatally stabbing a policeman. The group, responsible for numerous bloody attacks around the globe, has previously claimed certain attacks in a show of opportunism.

The man who launched Wednesday's attack at parliament was born in Britain and known to the intelligence services, Prime Minister Theresa May said on Thursday.

However, it said Masood had never been convicted of any terrorism offences and that he "was not the subject of any investigations and there was no prior intelligence about his intent to mount a terrorist attack".

"We still believe that Masood acted alone on the day", he said in a statement.

"This man got out of the vehicle with two knives in his hands and while he was running he was stabbing people".

Britain's domestic security agency, MI5, was criticised recently for losing track of a former Guantanamo detainee who won a payout from the British government for his detention and treatment in the prison camp and later blew himself up and injured several others.

In the aftermath of atrocities in France a year ago, London's most senior police officer warned that an attack was "highly likely" - a case of "when, not if." .

Thousands gathered during a candlelit vigil at Trafalgar Square in London on March 23, where a moment of silence was observed.

Rowley said 29 people have been hospitalized, seven of whom were in critical condition.

The U.S. Department of Homeland Security said it is in close contact with British authorities, but that the U.S. domestic security posture remains unchanged.

Aysha Frade, a British national whose mother is Spanish, was one of two people killed on the bridge.

The gunfire was heard at 2:38 p.m. London time inside the House of Commons as lawmakers were debating legislation on pension reform.

Barker said it was too early to predict the consequences of Wednesday's events but an attack by Islamic State sympathisers in San Bernardino, California, in 2015 had triggered a campaign pledge by now-President Donald Trump to ban Muslims from entering the United States.

May underscored that the attack targeted "free people everywhere", and she said she had a response: "You will not defeat us". Just this weekend, hundreds of armed police took part in an exercise simulating a "marauding" terrorist attack on the River Thames.

  • Salvatore Jensen