A far-right extremist waved his knife at horrified onlookers and warned they had "better move back" as he killed MP Jo Cox, a court has heard.
Thomas Mair, 53, is on trial at the Old Bailey accused of repeatedly shooting and stabbing the 41-year-old Remain campaigner a week before the EU referendum vote.
The mother of two was set upon outside her constituency surgery in Birstall, near Leeds, in front of her staff and shocked residents on 16 June.
Her assistant stepped in and hit the man with her handbag, while 78-year-old Bernard Carter-Kenny desperately tried to intervene but was stabbed too, the trial has heard.
An eyewitness described how the man "just walked away with not a care in the world".
Another witness, taxi driver Rashid Hussain, pulled up at around the same time as Ms Cox's arrival at Birstall library in a silver Vauxhall Astra.
As he was giving his fare her change, he heard what sounded like a "firecracker", jurors were told.
Mr Hussain demonstrated in the witness box how the man had stabbed Ms Cox five or six times in front of him.
He said: "When I reached near, he stepped back.
"I said: 'What are you doing? What's wrong with you?'
"He said: 'Move back, otherwise I'm going to stab you.'
"He was standing there with two ladies and another man. He said 'better move back.'
"He shot twice. He moved back and shot again."
Mr Hussain told jurors that by this point Ms Cox, who he had recognised as his MP, was bleeding from her mouth and was being helped by an Asian woman.
He said: "Jo's head was in her lap and she was pleading for Jo to stand up, talking about her kids.
"Her hands and clothes were covered in blood. She was the only person there helping her."
Clarke Rothwell was in a nearby sandwich shop when he heard a "popping" noise and a woman scream.
Ms Cox then slumped to the floor before she was shot in the stomach, he said.
The man shouted words like "this is for Britain" and "put Britain first" before reloading his gun and shooting for a third time, the witness told jurors.
Tracy Bywood saw the killing as she was washing up in a care home kitchen overlooking the scene.
She said the MP "went down on the floor like a sack of potatoes", adding: "It was so awful to see a woman have such animosity shown towards her."
Fighting back tears, she told the court: "I known it was a popping noise because I won't even buy Pringles any more, I can't handle the noise of the seal breaking."
Jack Foster told the court he saw the man, having shot Ms Cox once, reload his gun before shooting her twice more.
The England fan, who was wearing a red Three Lions football shirt ahead of a Euro 2016 game that evening, told how he shouted "f***ing leave her alone" but he took no notice.
"He reloaded his gun again, putting two cartridges in, cocked it and shot her on the floor," Mr Foster said.
He told the court he and two other men followed the man into a nearby street.
Mr Foster added: "He casually walked off. No remorse, no nothing."
Julie Holmes, who witnessed the attack from her shop, It's A Cake Thing, on Market Street, told how Ms Cox's killer looked straight at her as if to say "here I am".
She said: "He took a step into the road and he looked around and he looked over to where I was standing.
"He looked me right in the eye and lifted the gun, not pointing it at me but as a gesture, saying 'here I am'."
David Honeybell, who had gone to see Ms Cox before her surgery, told jurors: "He just walked away with not a care in the world, he just walked away."
Another eyewitness, Stephen Connolly, said: "It was very cold, he just walked away."
Mair denies Ms Cox's murder, possession of a firearm with intent to commit an indictable offence and possession of an offensive weapon - a dagger.
He also pleads not guilty to causing grievous bodily harm with intent to Mr Carter-Kenny on the same date.
The trial continues.