The London attack terrorist was named by the Metropolitan Police as Khalid Masood.

The 52-year-old married father of 3 was also known as Khalid Choudary.

UK Prime Minister Theresa May on Thursday said the attacker was British-born and had previously been investigated by MI5 "in relation to concerns about violent extremism."

May said there was "no prior intelligence" about Wednesday's attack on Westminster.

See our updated coverage of Masood's background here.

LONDON — The Metropolitan Police named the man behind the terrorist attack on Westminster in the capital on Wednesday, as Khalid Masood, who was also known as Khalid Choudary.

He was a 52-year-old married father of three children, and was a bodybuilder.

He was shot dead by police after killing an officer with a knife. Moments earlier he ploughed into pedestrians on Westminster Bridge in a 4x4 vehicle.

He was born in Kent and had previously been investigated by MI5 over concerns relating to violent extremism.

It was not known he was planning Wednesday's attack, but police said in a statement he has a range of previous convictions for assaults, including grievous bodily harm (GBH), possession of offensive weapons, and public order offences. He has not been convicted for any terrorism offences.

Earlier on Thursday, UK Prime Minister Theresa May said Masood, who was the unnamed at the time, had a history of extremism, and was known to police and intelligence officials.

In a speech in Parliament on Thursday, May acknowledged that the "whole country" would want to know the identity of the attacker but said he would not be named while investigations continue.

In an update earlier Thursday morning, Metropolitan Police Acting Deputy Commissioner Mark Rowley urged the media to avoid naming the man while the investigation was at a "sensitive" stage.

The police have conducted raids at six addresses, including in Birmingham, and made eight arrests. Rowley reiterated that the attacker was "inspired by international terrorism" and said he was confident the person acted alone.

Channel 4 names the wrong man

The attacker was briefly identified by Channel 4 News on Wednesday evening as a prominent British-born Islamist extremist, but the broadcaster later reversed its report after other journalists disputed it on Twitter.

BBC Pakistan correspondent Secunder Kermani said a "reliable source" told him the man Channel 4 named was in jail. ABC journalist Rym Momtaz echoed this account, saying she had spoken with the person's solicitor on Wednesday.

Channel 4 News later acknowledged the error made in its 7 p.m. bulletin. Editor Ben de Pear said award-winning reporter Simon Israel named the wrong man, but he did not apologise for the mistake. A repeat of Channel 4 News on Channel 4+1 at 8 p.m. was taken off air for about 40 minutes so the mistake did not air twice.

—Ben de Pear (@bendepear) March 22, 2017

A Press Association photographer took images of the suspect in the attack receiving medical assistance outside the Palace of Westminster. Sprawled metres away from the slain police officer, the man died from his gunshot wounds.

Moments earlier, a police officer could be seen standing over the man with his firearm. He appeared to be standing on a knife, possibly the one used in the attack.