Police are considering tightening security at Central Park and other areas where pedestrians, bicyclists and vehicles are close together in the wake of this week's terror attack in lower Manhattan, officials said Friday.

“Central Park is one we are taking a look at, sure,” NYPD Commissioner James O’Neill told reporters during his monthly crime briefing with Mayor Bill de Blasio.

O’Neill didn’t elaborate on what measures would be considered for the park or if it might be closed to vehicular traffic altogether.

Concrete barriers were installed along the West Street bike path on Thursday, along the same route where eight people were killed when terror suspect Sayfullo Saipov drove a truck onto the greenway, mowing down pedestrians and cyclists, officials said.

De Blasio said Friday that he had asked the NYPD and the Department of Transportation to assess other areas of New York City to fortify with barriers and to find the resources to install them -- not a small job in such a large city.

“There are going to have to be real choices here,” said de Blasio about the need to prioritize locations.

Meanwhile, ISIS has belatedly claimed responsibility for the attack, calling Saipov a "soldier of the Caliphate" and saying the rampage was in response to its call to target "citizens of the Crusader countries involved in the alliance against the Islamic State." 

The militant group made the claim in a weekly issue of its Al-Naba newspaper, but did not provide any proof it was involved in the plot.

Saipov was arraigned on federal charges on Wednesday, including one count of providing material support to ISIS, according to a criminal complaint. He was held without bail.

"In the short period of time since the attack, as alleged in the complaint, we have developed evidence establishing that Saipov committed this attack in support of ISIS," Joon Hyun Kim, acting U.S. attorney for the Southern District of New York, said. He called Saipov a man “consumed by hate and a twisted ideology” who was fully cooperative with authorities and talked proudly of what he had done.

Here's what we know about the attack and ongoing investigation, according to the NYPD, as well as state and local officials.

The attack

Saipov drove a rented Home Depot pickup truck onto the West Side Highway's bike path near Houston Street at 3:05 p.m., according to the complaint. He drove south on the bike path to Chambers Street, hitting cyclists and pedestrians before crashing into a school bus and emerging with a pellet gun and a paintball gun, the complaint said.

NYPD officer Ryan Nash, 28, shot Saipov in the abdomen, leading to his capture, officials said. Saipov was taken into custody and moved to Bellevue Hospital Center. 

While hospitalized at Bellevue, Saipov allegedly asked to display ISIS flags in his room, according to the complaint.

Eight people were killed and at least 12 were injured. Another three or four people, believed to be police officers, took themselves to the hospital, according to the FDNY.

After his arrest, Saipov told investigators he chose Halloween to maximize casualties and that he was "happy" he carried out the rampage, authorities said on Wednesday.

The victims

Of the eight people killed, one was a New Yorker, another was from New Jersey, five of them were Argentine tourists and one was a Belgium citizen, officials said.

Nicholas Cleves, 23, lived with his mother inside an apartment building on Greenwich Street, near Barrow Street, in Greenwich Village. He was the youngest of those killed.

Darren Drake, 32, lived with his parents in New Milford, New Jersey, and commuted to work at 7 World Trade Center for Moody's Investors Service, according to his father, Jimmy Drake, who described his son as his best friend.

The Belgium citizen was identified by the NYPD as Anne Laure Decadt, 31.

The Argentines -- identified as Hernán Diego Mendoza, Diego Enrique Angelini, Alejandro Damián Pagnucco, Hernán Ferruchi and Ariel Erlij -- were in the city celebrating the 30th anniversary of their high school graduation, the country's consulate said. 

"They were so happy to be together to have the opportunity to share some excellent moments," Mateo Estreme, consulate general of Argentina, said on Wednesday. "And then this terror attack brought an abrupt end to that celebration."

Estreme said he was working to ensure the Argentinian victims were returned home as soon as possible in order for family members "to have an opportunity to say goodbye to them." 

Another Argentine was one of the people injured. Two children and two adults on the school bus were also among the injured. 

Nine of the 12 people injured remained at hospitals Wednesday morning, four of whom were in critical but stable condition, FDNY Commissioner Daniel Nigro said at a news conference. 

The suspect

Saipov is a native of Uzbekistan who moved to the United States legally in 2010 and currently lives in Paterson, New Jersey.

He seemed a regular guy, said Carlos Batista, who lives two doors down from where Saipov lived with his wife and children. He was quick with a friendly wave, Batista said. Another neighbor said Saipov could often be seen bringing one of his daughters to her kindergarten class.

“He was a nice guy. He’d say ‘hey’ and wave when he drove past,” Batista said.

On Tuesday, FBI agents with K-9’s swarmed the squat, brick building where Saipov lived in a working-class section of Paterson with a large population of immigrants from the Middle East and Spanish-speaking countries.

Worshippers at Paterson’s Omar Mosque, around the corner from Saipov’s apartment, said they didn’t know Saipov and stressed Islam is a peaceful religion.

“Nobody’s ever seen this guy,” said Ramy Elhelw, 30, of Hoboken, who described the mosque community as tight-knit. “Nobody knows him.”

Before moving to New Jersey, Saipov lived in Florida and Ohio, a law enforcement source said. He married Nozima Odilova in 2013 when she was 19, according to published reports. At the time he worked as a truck driver.

Recently, Saipov drove for Uber, company officials said Wednesday night.

Sources said Saipov’s wife has been questioned by federal agents and is not believed to have been involved in her husband’s alleged terror plot.

Records show he set up two businesses with Ohio addresses in 2011 and 2013, though it’s unclear if he was living in the state at the time.

The latest on the investigation

A top police official said on Thursday that capturing Saipov alive could lead authorities to a better understanding of how people in the United States become radicalized.

“When you capture a live terrorist you have the ability to question that person and you’re able to glean a lot,” said John Miller, the NYPD’s deputy commissioner of intelligence and counterterrorism.

Investigators can learn whether the person acted alone or was part of a network, or whether the person communicated with a terror network online or through encrypted message, Miller said on “CBS This Morning.”

“But you can also go deeper into those questions about what brought you to this point,” Miller added. “And there are former defendants in cases like this where we’ve learned a lot about the arc of their radicalization."

Questioned by the hosts about how to change that arc, Miller said authorities are working on that and have reached out to the Muslim community, but conceded, “We have no effective counter message today.”

After his arrest, Saipov waived his Miranda rights during an interview at Bellevue Hospital Center and told investigators that he was inspired to carry out the attack after watching ISIS videos on his cellphone, the criminal complaint said. 

He started planning an attack in the United States about a year ago, but zeroed in on New York City as his target about two months ago, per the complaint. A law enforcement source said Saipov came to Manhattan four times before the attack in what were believed to be reconnaissance missions.

He appeared to follow ISIS instructions for terror attacks found on social media “almost to a T,” Miller said.

He rented the pickup truck at 2:06 p.m. Tuesday from a Home Depot in Passaic, New Jersey. He then drove over the George Washington Bridge and, just after 3 p.m., he entered the West Side Highway bicycle path, police said.

Saipov yelled "Allahu Akbar," Arabic for "God is great," as he exited the truck, the complaint said. A black bag containing three knives and a wallet, which had Saipov's Florida driver's license inside, was found near the truck, per the complaint. 

Investigators also found handwritten notes in Arabic that said, in part, "No God but God and Muhammad is his Prophet," and "Islamic Supplication. It will endure," which is a common phrase used to refer to ISIS, according to the complaint. A stun gun and two cellphones were also recovered from the floor of the truck.

Investigators found about 90 videos on one cellphone, many of which appeared to be ISIS-related propaganda, the complaint said. On the other phone, searches for truck rentals and Halloween in New York City were discovered.

Saipov had also wanted to continue his rampage by heading to the Brooklyn Bridge and considered putting ISIS flags on the front and back of the truck during the attack but decided not to because it would draw too much attention, per the complaint.

“In many ways, this was now a classic case of a radicalization of a domestic jihadist who associated with ISIS, and this is their new playbook,” Gov. Andrew Cuomo said on “CBS This Morning” Wednesday.

Investigators were looking into whether Saipov had ties to people connected to ISIS, according to the New York Times. A person at a wedding that Saipov attended in Florida was under scrutiny by the FBI, but it's unclear why, the paper reported. 

Miller said Saipov had never been the subject of an FBI or NYPD probe.

During his arraignment Wednesday, Saipov's attorney, David Patton, who heads the federal public defender program in Manhattan, said his client was “in a significant amount of pain” and asked Magistrate Barbara Moses to order “pain management” while he's is in custody. Moses said she would suggest it to prison authorities.

Saipov wore an earpiece and was accompanied by a Russian interpreter but answered “Yes, M’am” when the judge asked him if he was able to understand the translator.

Later outside of court, Patton made a pitch for fair treatment, asking the public to allow “the judicial process [to] play out. It's especially important in a case like this. I promise you that how we treat Mr. Saipov in this judicial process will say a lot more about us that it will say about him.”

FBI stops search for person of interest

The FBI is no longer looking to speak with Mukhammadzoir Kadirov, 33, in connection with the attack, the agency said. The FBI had put out a photo of Kadirov on Wednesday.

"There is no longer a need for me to seek a name anymore. We have found him," FBI Assistant Director in Charge William F. Sweeney, Jr. said at a Wednesday news conference, but declined to offer more information.

Kadirov is a native of Uzbekistan. Sources said Thursday that Kadirov was an acquaintance of Saipov’s who was wanted for questioning about what he knew about Saipov. Kadirov was quickly located, questioned, not charged with any crime, and let go, the sources said.

With Newsday, Reuters and Lisa Colangelo