An imam guarded the van driver who mowed down Muslim worshippers until the police arrived, telling a crowd: “Do not touch him.”
Mohammed Mahmoud was said to have used his body to shield the suspected terrorist, who had been wrestled from his vehicle, from the fury of onlookers.
The attacker had been acting violently as he was restrained and allegedly told the injured: “You deserve it.”
Witness Hussain Ali also claimed the suspect was smiling and waving as he brought carnage to Seven Sisters Road in Finsbury Park, north London.
The imam was hailed as the “hero of the day” by Toufik Kacimi, chief executive of the Muslim Welfare House, outside which the attack took place.
Mr Kacimi arrived an hour after the attack and spoke in detail to Mr Mahmoud about the scenes of horror.
He told the media: “An old man has passed away, what for? What did he do? He was just coming out of prayers, a nice gentleman going home after prayers and he is hit and killed by a car - what did he do? Why? Why?
“The guy, he came out and said ‘You deserve, I did my bit, you deserve it’ and he was shouting and screaming abusive language - what for? What did he do, this man? He is an innocent man.
“I spoke to the eyewitness who caught the man and kept him safe, stopped him from being harmed by the local group that he attacked.
“Our imam, Mohammed Mahmoud, contained the guy - he was very violent. He contained him with two or three other guys and gave him to the police once they arrived.
“They were worshippers. A man was taken ill and they were trying to help him, that is why there was a large crowd and visibly you can tell people are Muslims, I am not going to say the countries but they were clearly Muslim.
“He saw a crowd of people and drove with speed into them.
“Mohammed was the hero of the day, he was the one who contained the guy and held him up until the police came and took him away.
“He explained to me that the man was very violent, aggressive, and he came over him until the police arrival - but there were other people helping him because the crowd was extremely angry, unhappy, so some people started acting violently too.
“”He is in terrible shock, of course, he didn’t see the man die but he did see the man grabbed by the local community.
“When I arrived here it was like a war zone. The crowd, they did not understand what was going on. It was a lot of police, a terrible scenario really - I hope it will never happen again.
Mr Ali, 28, said a man in a wheelchair was among those hit by the speeding vehicle.
He said: “The leader of the mosque said ‘You do not touch him’. He was sitting and holding him like that, people kept holding him.
“All the police and helicopters came after around eight minutes.”
Describing the horrifying scene which unfolded outside the Islamic centre early on Monday morning, he continued: “All I heard was a banging, then I turned and saw all the shouting and running.
“I saw people taking a man from underneath the van, he was black, bleeding, he was not dead, he was alive.
“There was a man in a wheelchair, a man underneath the van, it was hell.
“People who were inside saw the attacker was smiling, he was waving, he was happy.
“It was panic, people were shouting, screaming, some saying it was an accident.
“It was panic, it was horror.”