He emerged from the rented white truck holding what appeared to be two guns - but turned out to be a paintball and pellet gun - and ran around before being shot by a policeman.
The "hero" officer has been named as Ryan Nash, 28, who was only in the area after being called to investigate reports of a suicidal teenager.
Saipov underwent surgery after he was apprehended and remains in hospital. As well as the eight people who died, 13 were injured.
As officers pursued leads in the first terror incident to hit America in Donald Trump's time in the White House, the president was pointing the finger of blame at political rivals.
Trump criticised the scheme that reportedly let Saipov move to the country - the Diversity Visa Lottery Program - and the support for it from the Democrats.
Trump said the suspect is an "animal" and says he will fight to end the visa program.
Trump said he'll ask Congress to "immediately" begin work to terminate the program, which the alleged attacker used to enter the United States.
"We will take all necessary steps to protect our people."
In particular Trump singled out Chuck Schumer, the New York Senator who leads the Democrats in the Senate, for criticism, calling the scheme "a Chuck Schumer beauty".
Schumer hit back, tweeting that it is never "too soon to politicise a tragedy" and calling on Trump to scrap cuts to "anti-terrorism funding".
Trump also vowed to "step up" his extreme vetting program on border checks in a tweet, adding: "Being politically correct is fine, but not for this!"
Speaking before a Cabinet meeting at the White House, Trump said "all of America is praying and grieving" with the victims.
"Our hearts break for them."
Later responding to a shouted question about sending the Saipov to Guantanamo Bay prison in Cuba Trump said "I would certainly consider that. Send him to Gitmo".
On Tuesday afternoon, Trump announced he wanted Congress to shut down the Diversity Visa Lottery Program, replacing it with a "merit" based system.
Uzbekistan, Saipov's home country, is not on a list of nations which Mr Trump has introduced automatic tighter immigration controls on.
Saipov's links to Isis are being closely examined. He reportedly left behind a note in the truck he used for the attack citing his support for the jihadist terror group.
However, a firm link to the group is yet to be established, leading to suggestions that Saipov was radicalised during his time in the US.
Andrew Cuomo, the New York governor, said on Tuesday: "He was associated with Isis. He was radicalised domestically."
Meanwhile, chilling online postings from Islamic groups in the run-up to the attack have raised suspicions about the level of forethought.
One photo posted on an Isis-linked Twitter page before the attack appears to have been taken in the same spot in Manhattan where the truck mounted the bike path.
The image, which shows the 1 World Trade Center in the background, was taken posted two months ago according to the respected SITE group which monitors terror activity.
At a press conference on Tuesday, New York police and politicians gave fresh details about the attack and the suspect's links to jihadist groups.
It took just four minutes for the attacker to mount the bike path, drive around a mile along the bike path and smash into a school van, according to a timeline from police.
A note was found in the truck written in the Arabic praising Isis, with an officer saying the "gist" of the note was "the Islamic State would endure forever".
An official said that the suspect "appears to have followed almost exactly to a tee" instructions Isis posted online about using vehicles for terror attacks.
Bill De Blasio, the New York mayor, praised the spirit and resilience of the city's people and urged them to go about their lives as normal.
He said: "We understand this was an attack on our values. It was an effort to breqak our spirit. But as an effort to break our spirit it failed.
De Blasio added: "Be New Yorkers. Be strong, be proud, be resilient. Show the whole world right now that we will not be moved by terror."
