The man suspected mastermind of the attack in Westminster, London has been named as Khalid Masood.
Metropolitan Police said Masood, who was shot dead by an officer, was not the subject of any current police investigations, but had a range of previous convictions for assaults.
The 52-year-old was born in Kent and was believed to have been living in the West Midlands, BBC reports.
Police said there had been no prior intelligence about Masood’s intention to carry out an attack.
However, he was known to the police and his previous convictions included possession of offensive weapons and public order offences.
His first conviction was in November 1983 for criminal damage and his last conviction was in December 2003 for possession of a knife.
He had not been convicted of any terrorism offences.
Meanwhile, the Islamic State group has said it was behind the attack.
Others killed in Wednesday’s attack were Keith Palmer, Aysha Frade and American Kurt Cochran.
Already, eight arrests have been made in London and Birmingham.