Amid the chaos and agitation surging through a crowd early Monday after a van plowed into pedestrians outside London's Finsbury Park Mosque, one person stepped in to protect the attacker, witnesses say: the mosque's imam.

Imam Mohammed Mahmoud tried to keep members of the crowd at bay and was being called a hero.

The van slammed into worshipers leaving the mosque after midnight Ramadan prayers, killing one person and injured 10 others. British Prime Minister Theresa May said police were investigating the incident as a terrorist attack.

In the tense moments after the attack, some pedestrians pushed the 48-year-old suspect to the ground, The Guardian reported, and Mahmoud, an imam from the Muslim Welfare House, pleaded for calm.

Toufik Kacimi, the mosque's chief executive, said the imam “helped calm the immediate situation after the incident and prevented further injuries and potential loss of life,” according to the Guardian.

Witness Hussain Ali, 28, told the Press Association that "the leader of the mosque said 'You do not touch him."

"He was sitting and holding him like that, people kept holding him," Ali said.

Mamhoud was joined by several other bystanders who formed a protective ring around the suspect until police hustled him into the back of a van, the Evening Standard reported.

“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," Kacimi told the Standard.

Monday morning the Muslim Welfare House headlined its website with this message: "All of us at Muslim Welfare House sends our thoughts and prayers to the victims and those injured in the major incident at Finsbury Park. The Muslim Community in this area is horrified at this incident and is concerned and shocked at the events."