It took a few split seconds before anyone understood what was happening as they watched a truck pick up speed on a busy bicycle path, smashing cyclists and leaving a trail of mangled bikes and bodies on Tuesday afternoon.
The truck continued to mow down anyone and anything in its path until it came to a halt after colliding with a school bus, which left two adults and two children inside injured.
The driver then got out of the pickup truck, shouting "Allahu Akbar" (God is great) and brandishing two guns later found to be a paintball gun and a pellet gun.
There were loud screams as people scattered in panic as police arrived at the scene.
"Oh my God, I just heard gunshots and ran with my dog," singer-songwriter Josh Groban, who was walking his dog in the area, tweeted seconds after the police shot the driver.
Student Tawhid Kabir from the Borough of Manhattan Community College told reporters: "We heard gunshots and we all went down; we were all scared."
The driver, Sayfullo Saipov, a 29-year-old from Uzbekistan who holds a green card, lives in New Jersey with his wife and three children. He had rented the pickup truck from Home Depot, a chain store. He is in hospital and speaking to interrogators, reports say.
VEHICLES TURNED WEAPONS OF TERROR
AUG 17, BARCELONA: A driver runs a van into crowds on the popular Las Ramblas Boulevard. It is followed hours later by a car attack in the seaside town of Cambrils. Fifteen people are killed. All terror cell members are either killed or arrested.
AUG 12, CHARLOTTESVILLE: At a far-right rally in Charlottesville, Virginia, a woman, 32, is killed when a car rams into a crowd of counter-protesters.
JUNE 19, LONDON: A van is driven into a crowd of Muslim worshippers near a mosque in the Finsbury Park area, killing a man and injuring 11 others. A man, 47, is arrested and charged with terrorism-related murder and attempted murder.
JUNE 3, LONDON: Three attackers hit pedestrians with a van and go on a stabbing spree in the London Bridge area. Eight people are killed before the assailants are shot dead by police. The attack is claimed by the Islamic State in Iraq and Syria.
MARCH 22, LONDON: A British convert to Islam, Khalid Masood, 52, mows down pedestrians on Westminster Bridge and stabs a policeman, killing five people and injuring about 50 before being shot dead by police. The attack is claimed by ISIS.
AUG 19, PARIS: A 36-year-old Algerian man named as Hamou B. drives a BMW into a group of soldiers outside a barracks in the western Paris suburb of Levallois-Perret, injuring six. The suspect is shot.
JULY 14, 2016, NICE: Tunisian Mohamed Lahouaiej-Bouhlel, 31, ploughs a 19-tonne truck into a Bastille Day crowd, killing 86 people. ISIS later claims Bouhlel as one of its followers.
APRIL 7, STOCKHOLM: Uzbek national Rakhmat Akilov, 39, confesses to using a stolen beer truck to mow down pedestrians on the city's busiest shopping street, Drottninggatan, killing five people.
CHAOS AT THE SCENE
Oh my God, I just heard gunshots and ran with my dog.
SINGER-SONGWRITER JOSH GROBAN, who was walking his dog in the area, tweeted seconds after the police shot the driver.
The bicycle path, where the truck wreaked havoc, is one of the busiest in New York.
At the end of the roughly two to three minutes of horror, six people were dead and two others later died in hospital. Nine remain in hospital, four in critical condition.
Among the dead were a Belgian and five Argentinians who were in New York for a school reunion.
Singapore was among the countries that condemned the attack yesterday. "Singapore strongly condemns the terrorist attack in New York City... that killed and injured innocent people," the Ministry of Foreign Affairs said in a statement. "We express our heartfelt condolences to the families of the victims, and wish the injured a swift recovery."
It also advised Singaporeans in New York to be alert and vigilant.
Armed police stepped up their presence in crowded areas of Manhattan after the attack.
The annual Halloween parade took place on Tuesday night under heavier security, as the spire of the Empire State Building was lit up in the red, white and blue of the American flag.
Yesterday morning, the New York Stock Exchange observed a minute's silence for the victims.
President Donald Trump called for extreme vetting and blamed Democrat Senator Chuck Schumer for what he called "Democrat Lottery Systems". "We are fighting hard for Merit-Based immigration, no more Democrat Lottery Systems. We must get MUCH tougher (and smarter)," he tweeted.
Mr Schumer said in response that he continued to believe immigration was good for America, and that the President should not politicise the tragedy and divide Americans.
Speaking to CNN, New York City Mayor Bill de Blasio said: "The last thing the President or anyone should do is politicise this tragedy."
He added: "Anyone who wants to come to this country should be very thoroughly vetted as an individual, but the minute you start generalising it, especially to a whole religion, then, unfortunately, we are sending the exact negative message that a lot of our enemies want sent."
Uzbekistan has never been included in a list of Muslim-majority countries whose people the Trump administration has attempted to block from entering the US.
Regardless, most experts say banning travel to the US from select countries will do nothing to stop people who are already in the US from being radicalised.
"This ideology... does not require a visa or go through airports," Mr Ali Soufan, the New York-based chief executive of Soufan Group, told The Straits Times. "As long as we have people who are attracted and inspired by it, we're going to have a threat."
He also warned against an overreaction. The attack came just days after the Islamic State in Iraq and Syria suffered significant battlefield defeats in the Middle East.
"Unfortunately, the 'inspirational' message of these terror groups will definitely outlast any territorial or physical losses they may have suffered," he added.