The London police officer stabbed to death by an attacker after he ploughed into pedestrians on Westminster Bridge has been identified as Keith Palmer.
The knife-wielding assailant, who has not been named, had entered the gates of Parliment when he stabbed the 48-year-old husband and father.
Police shot the attacker dead soon after as he tried to make his way into the Palace of Westminster building. Three others were killed in the attack.
Conservative MP Tobias Ellwood, whose brother was killed in the Bali terror attack in 2002, performed first aid on Palmer, but he could not be saved.
Constable Palmer had served with the Metropolitan Police Service for 15 years and was a member of the specialist parliamentary and diplomatic protection command.
Metropolitan Police Service acting deputy commissioner Mark Rowley identified the officer, who was unarmed when he was killed.
"Today in Westminster we saw tragic events unfold and our thoughts are with those who lost loved ones, those who were injured and all those affected by this attack," Rowley said.
"(Palmer) was someone who left for work today expecting to return home at the end of his shift, and he had every right to expect that would happen."
Rowley added that another three police officers were among the injured, two of whom were in a serious condition.
James Cleverly, a British MP who said he had known Mr Palmer for 25 years tweeted of his heartbreak among the outpouring of grief for the victims.