Four people have died, two remain in hospital in a critical condition and dozens more are injured.
As each day goes by, more details surrounding the horrific attack in Westminster are emerging.
Here’s what we know on Friday night.
More details about the attacker have emerged
At school, Khalid Masood – born Adrian Russell Elms – was known to be a keen footballer, yet grew into a troubled adult who spent time in and out of prison.
Some reports suggest his radicalisation happened during one of his stints behind bars, though others suggest it was while he allegedly spent time in Saudi Arabia.
Masood’s criminal record dated back to 1983 and included convictions for assault, GBH and possession of an offensive weapon, leading him to spend time at Lewes Prison in East Sussex, Wayland Prison in Norfolk and Ford open prison in West Sussex.
At some point after his radicalisation he came to the attention of MI5, 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 continue to hunt for possible associates.
Counter-terrorism detectives continue to trace any associates of Masood, after arresting 11 people.
Of the 11, only four remain in custody on suspicion of preparation of terrorist acts – two men aged 27 and 58 who were arrested in Birmingham on Thursday, and a 32-year-old woman and a 35-year-old man who were arrested in Manchester on Friday.
The other six who were arrested have been released and face no further action.
Muslim leaders united to condemn the attacks.
Muslim leaders called the attacks “heinous and appalling” as they joined with Christian and Jewish counterparts to lead a minute of silence.
Sheikh Mohammed Al-Hilli, representing Shia Muslims, and Sunni Sheikh Khalifa Ezzat, head imam at the London Central Mosque, stood side-by-side with Justin Welby, Ephraim Mirvis and Cardinal Vincent Nichols outside Westminster Abbey.
MP Tobias Ellwood has been recognised for his heroic efforts.
Fellow MPs, police and the public hailed Ellwood a hero following his efforts to save the life of Pc Keith Palmer, who had been stabbed.
Downing Street announced Ellwood and security minister Ben Wallace were to be honoured by the Queen, who approved the appointment of the pair to the Privy Council.
This means Ellwood and Wallace will now be referred to as ‘Right Honourable’ and receive top-secret national security briefings as members of the Privy Council.