A far-right extremist told police "it's me" before he was rugby tackled to the ground after the killing of Labour MP Jo Cox, a court heard.
Thomas Mair, 53, is accused of repeatedly shooting and stabbing the 41-year-old Remain campaigner a week before the EU referendum vote in June.
Cox was set upon outside her constituency surgery in Birstall, near Leeds, in front of her staff and shocked passers-by.
Her assistant stepped in and hit Mair with her handbag while 77-year-old Bernard Carter-Kenny desperately tried to intervene but was stabbed too, the Old Bailey heard.
Throughout the "cowardly" killing, the defendant was heard to rant "Britain first", prosecutor Richard Whittam QC has told jurors.
The gardener, who had looked up right-wing literature in his local library, was arrested a mile away from the attack, jurors were told.
Pc Craig Nicholls was on mobile police patrol with Pc Jonathan Wright in Risedale Avenue where they arrested Mair.
The unarmed officers had been given a description of a man to look out for who was suspected of being involved in a shooting.
Pc Nicholls told jurors they spotted a suspect matching the description just after 1.30pm in nearby Leeds Road carrying a black holdall.
Pc Nicholls turned their vehicle into a cul-de-sac and saw the man in the middle of the road.
His colleague leaned out and ordered him "several times" to put the bag down and show his hands.
The West Yorkshire Police officer told jurors: "He dropped the bag to his right hand side. He turned around and it was very quick, put his hands into his pockets.
"I just remember seeing loose change fall out of his pockets. At that point he put his arms out and said 'it's me'."
The officer told jurors they then "rugby tackled him to the ground".
The defendant then told officers "I'm a political activist", the officer said.
Simon Russell Flint QC, for Mair, suggested the defendant did not shout "It's me" or claim to be a political activist and had remained silent throughout his arrest.
The lawyer also asserted that Mair said nothing about having a gun, and suggested one of the officers commented "We are going to get into trouble for this", but Pc Nicholls denied it.
Pc Wright later echoed his colleague's account of Mair's arrest.
Jurors were shown images from the scene of Mair's arrest, including the black holdall containing the sawn-off German-made .22 rifle prosecutors allege was used in the murder.
Mair denies Cox's murder, possession of a firearm with intent to commit an indictable offence and possession of an offensive weapon - a dagger.
Mair also pleads not guilty to causing grievous bodily harm with intent to Mr Carter-Kenny on the same date.