British officials — including Queen Elizabeth — are praising the heroism of those who helped curtail a deadly terror attack as it unfolded in the heart of London on Friday. Bystanders — wielding a fire extinguisher and what reports say was a narwhal tusk — chased after the man who stabbed several people while he was wearing what police have called a hoax suicide vest.

Videos from the scenes showed a group of bystanders spraying fire retardant at the knife-wielding attacker and pinning him on the ground until police arrive. Officers shot and killed the attacker, now identified as convicted terrorist Usman Khan.

Several of the bystanders were attending an event at historic Fishmongers' Hall near London Bridge for Learning Together, a prisoner rehabilitation program affiliated with Cambridge University, when the attack started, according to the Metropolitan Police. Khan, who was released from prison in 2018, was also in attendance, the BBC reported.

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Amy Coop, who said she was also at the event, wrote on Twitter that a man at Fishmongers' Hall took a five-inch narwhal tusk from the wall and "went out to confront the attacker. You can see him standing over the man (with what looks like a white pole) in the video. We were trying to help victims inside but that man's a hero."

Police officers patrol the scene of the deadly stabbings at London Bridge, in London, Saturday, Nov. 30, 2019. UK counterterrorism police on Saturday searched for clues into how a man imprisoned for terrorism offenses before his release last year managed to stab several people before being tackled by bystanders and shot dead by officers on London Bridge. Alberto Pezzali/AP

One civilian, a tour guide named Steve Hurst, told the BBC he was near the attack when he decided to help. He joined the group trying to restrain Khan, and kicked him in an effort to make him drop the knife.

"We saw that the knife was still in his hand... I just put a foot in to try and kick him in the head," Hurst said. "We were trying to do as much as we could to try and dislodge the knife from his hand so he wouldn't harm anyone else... The guys that were there were absolutely amazing. Heroes beyond belief."

Another tour guide, Thomas Gray, told NBC News he was driving on the bridge when he stopped and joined the group. "I asked what was going on and they said the guy just stabbed two women back there," Gray said. According to Gray, the attacker had a knife in both hands. Gray said he stomped on the attacker's wrist, forcing him to drop one of the large knives.

London Mayor Sadiq Khan commended the "breathtaking heroism" of the civilians "who literally ran towards danger."

"We saw Londoners, ordinary citizens, acting in an extraordinary way," the mayor said shortly after the attack. "I want to say thank you to them on behalf of all Londoners."

"They improvised in relation to trying to take weapons off him and stop him from harming others. Whether it's using a fire extinguisher, whether it's using a whale's tusk, whether it's using other devices," he told reporters.

In a written statement, Prime Minister Boris Johnson said he wanted "to pay tribute to the extraordinary bravery of those members of the public who physically intervened to protect the lives of others."

"They represent the very best of our country and I thank them on behalf of all our country," he added.

Queen Elizabeth II also issued a statement offering condolences to the families of the victims and praising those who intervened.

"I express my enduring thanks to the police and emergency services, as well as the brave individuals who put their own lives at risk to selflessly help and protect others," the queen said.