The tourist attraction was cordoned off by police and suspected drunk-driver, Richard Rojas, 26, was arrested.
After the collision, Rojas raced past a screaming woman and child as he leapt from the smouldering wreck of his car.
An 18-year-old girl died and at least 22 other pedestrians were injured as the maroon Honda saloon mounted the pavement at the tourist hotspot.
Rojas, a US Navy veteran from the Bronx, allegedly had a history of drink-driving and one report claimed he was high on marijuana.
Rojas – reportedly described by a policeman as "drunk or on drugs" – was quickly grabbed by a traffic officer and pinned down with help of colleagues and members of the public. Police said he got into a fight with an officer.
A video later showed him, his shirt ripped, being led away.
One report claimed Rojas was "visually impaired" and had admitted to police he had been smoking marijuana before the crash.
The terror unfolded shortly before midday local time as Times Square was packed with tourists and office workers on lunch breaks.
Witnesses described how he careered along Seventh Avenue before making a U-turn against the traffic. He is said to have mounted the pavement and drove three and a half blocks, sending pedestrians flying, before crashing into bollards on the corner of 45th Street and Broadway.
The 18-year-old, named as Alyssa Elsman from Michigan, died at the scene. Her 13-year-old sister was taken to hospital. At least four victims suffered critical injuries including open fractures and a further three were described as seriously injured, police said.
On Twitter, Annie Donahey wrote: "The girl who was walking next to me died. If I’d waited to cross the street I’d probably be dead right now."
Witness Juan Soto told Sky News: "It was a gruesome scene with multiple victims on the sidewalk. When I saw the head injuries and their blood, and victims not moving, that’s when I realised a car had run into the crowds."
Rojas was previouslycharged with drunken driving in 2008 and 2015, according to New York City police. The state motor vehicle department confirmed he was convicted of driving while impaired in both cases but still had a valid driver's license as of Thursday.
It is believed he has also had his licence suspended "multiple times".
Fire Commissioner Daniel Nigro said Rojas was arrested for drink-driving in Queens in 2008 and held again for the same offence in Manhattan in 2015.
In May this year he was arrested for ‘menacing’, it was said.
Rojas returned from his Navy service with a drinking problem and had posted "crazy stuff" on social media, said a friend, Harrison Ramos, speaking to Reuters outside the apartment building where Rojas lives in New York City's Bronx borough.
"Don't make him out to be a terrorist or something," Ramos said. "He served his country and when he came back, nobody helped him."
Rojas attended college and works in real estate, Ramos said.
"He went through a real tough time," Ramos said, adding that he had lost contact with Rojas. "That's my friend. I care about him, and it hurts."
Only a week ago, Rojas was arrested at his apartment in the Bronx for threatening another man with a knife.
"Do you feel safe? You stole my identity," Rojas told the man, grabbing his neck in one hand while brandishing the knife in the other, according to a police spokeswoman. She did not have additional details about the incident.
He was charged with menacing and possession of a weapon, according to court records. He eventually pleaded guilty to harassment, a violation, and was not sentenced to any prison time.
Police have not yet announced formal charges against Rojas in the Times Square incident, and he had not yet appeared in court. It was not immediately clear whether Rojas had a defense lawyer.
Rojas enlisted in the Navy in 2011. He served as an electrician's mate fireman apprentice, mostly based in Florida.
While stationed in Jacksonville, Rojas was arrested for battery and resisting an officer without violence, both misdemeanors.
An arrest report from the Jacksonville Sheriff's Office said Rojas yelled at an officer, "My life is over," and threatened to kill police after his release from jail. He also told the officer that he had beaten a cab driver to whom he owed money and had been drinking at the time of the arrest, according to the report.
Court records indicate the charges may have been dropped.
Navy records show he spent two months in a military prison in Charleston, South Carolina, in the summer of 2013 but do not specify why.
He left the service in May 2014, according to records, which do not offer any additional details.
A few hours after the Times Square incident, about 20 police officers and detectives occupied the sidewalk outside the six-storey red brick building where Rojas lives.
Times Square is one of the busiest tourist spots in the world and some half a million visitors pass through it on busy days. New York Governor Andrew Cuomo called Thursday’s incident "horrific".
He added: "My heart goes out to the victims of this terrible tragedy, as well as their families."
Daily Mail and Reuters