A police officer attempted rugby tackling Westminster attacker Khalid Masood as he fatally stabbed Pc Keith Palmer, an inquest has heard.
Pc Nick Carlisle described the moment he came face to face with Masood as the attack took place on March 22 last year.
He told the inquest he had no doubt Masood "was coming to kill police" during his knife and car rampage in and around the Palace of Westminster.
Pc Carlisle was among the uniformed unarmed officers posted at the palace gates, and was just metres away when he heard a "loud bang".
Asked if he had any doubt what the attacker wanted to do, Pc Carlisle said: "None whatsoever.
"He looked me directly in the eye. He was coming through a crowd of people. He was not interested in members of the public.
"He was coming to kill police officers."
Describing the fast-moving events, he said: "I heard a loud bang in Bridge Street. It was over my right shoulder, about 30 metres away."
Through the radio he heard a report of a possible explosion, he said: "I could see a grey vehicle 4x4 against the wall of the railings in Bridge Street. Smoke was coming through the fence. It looked as if there had been a high speed road accident."
He said there was shouting and screaming as a crowd of people surged towards Parliament Square.
"A man wearing a suit in his 40s shouted 'men with knife stabbing people, men with knives,'" he said.
"As soon as he said that I was drawn to the attacker just behind."
Pc Carlisle said his colleague Pc Kevin Tipple reacted by shouting to "shut the gate" while Pc Palmer called to the crowd to "come in here".
He said the two events happened almost at the same time.
Pc Carlisle said he backed away about 10 metres and turned to see the attacker had caught Pc Palmer.
"I ran forward intending to issue a rugby tackle, shoulder barge."He came at me with knives up. I was very close," he said.
The distraction worked and gave Pc Palmer enough time to get up and run as Pc Carlisle shouted for "armed support", the inquest heard.
Pc Carlisle told how he saw close protection officers with handguns drawn.
"I indicated the suspect, making it clear who the attacker was and pointing him out," he said.
He said he did not hear the warning but understood there had been one before Masood was shot.
Afterwards, he secured him in handcuffs, fearing he was a "Jihadi-type" attacker who might was wearing a suicide vest.
He then saw Pc Palmer on the ground surrounded by a "gaggle of people" and went to help.
The inquest continues.