Lower Manhattan was brought to a standstill when a man driving a rented pickup truck ploughed into pedestrians and cyclists on a popular bike path along the Hudson River yesterday afternoon.
NYPD Deputy Police Commissioner John Miller said multiple knives were found in the truck.
Investigators say the suspect named as Sayfullo Saipov, 29, followed plans laid out by the militant Islamic State group and planned the attack weeks in advance.
Commissioner Miller said notes found in the vehicle were written in Arabic and said police are examining how the suspect is connected with subjects of other investigations.
Saipov, 29, who was shot and arrested by police moments after the rampage. He remains in hospital.

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The attack was the deadliest on New York City since September 11, 2001, when suicide hijackers crashed two jetliners into the World Trade Centre, killing more than 2,600 people. A further 12 people were injured, some critically, in Tuesday’s attack.
New York Police Commissioner James O’Neill said: “What happened yesterday was not okay. It was something that none of us will accept as inevitable.
“We have in the past prevented two dozen plots against New York City. But none of that matters when eight innocent lives are taken by a criminal committing a cowardly act driving a rental truck.”
New York’s Mayor said the city “will not blink” in the face of the “cowardly” terror attack.
Bill de Blasio, 56, told a press conference: “This violence was an effort to make us blink and we won’t blink. We won’t change.
“We will not be moved by terror.
“This was an attack on the United States of America, New York City and an attack on our people.
“This was the definition of terrorism. It was an attempt to take away people’s hope and spirit and to make them change.
“What New Yorkers showed already is that we will not change. We will not be cowed. We will not be thrown off by anything.
“This cowardly act targeted the most innocent people in the middle of the most innocent pursuits which was meant to make people feel they could not go about their daily lives.”
“What we saw last night was a million New Yorkers at the Halloween parade and as we spoke to them they were undeterred and strong. It made me very proud of New York City and the people of this country.
“This morning people went to work, kids went to school. Nobody thought they had any choice but to stand up to this of terror.
“As we now move forward, we give our prayers to the families of those were killed.
“We understand this was an attack on our values. It was an effort to break our spirit. But as an effort to break our spirit, it failed.”
US President Donald Trump took to Twitter to condemn the attack.
He said he would consider sending the suspect to Guantanamo Bay.
In one tweet he wrote: “In NYC, looks like another attack by a very sick and deranged person. Law enforcement is following this closely. NOT IN THE U.S.A.!”
Then later on he added: “We must not allow ISIS to return, or enter, our country after defeating them in the Middle East and elsewhere. Enough!”
In another message he wrote: “I have just ordered Homeland Security to step up our already Extreme Vetting Program. Being politically correct is fine, but not for this!”