NEW YORK — Authorities said Wednesday that the 29-year-old man accused of mowing down pedestrians and cyclists on a Manhattan bike path, killing eight people, plotted for weeks before carrying out the attack in the name of the Islamic State.

Officials identified the suspected attacker as Sayfullo Saipov, a legal permanent resident of the United States who arrived in the country from Uzbekistan in 2010 through a diversity visa program. They said Saipov was influenced by the Islamic State, also known as ISIS, and its violent tactics after coming to the United States.

Saipov left notes pledging his allegiance to the group, authorities said, though they have not identified any direct connections between Saipov and the organization.

[ Five old friends from Argentina reunited in New York. They died together in a terrorist attack. ]

These notes, which included symbols and words, were handwritten in Arabic essentially said “that the Islamic State would endure forever,” John Miller, the deputy New York police commissioner for intelligence and counterterrorism, said at a briefing on Wednesday. The Islamic State has urged its followers to use vehicles to carry out attacks.

“He did this in the name of ISIS,” Miller said. “He appears to have followed almost exactly to a T the instructions that ISIS has put out in its social media channels before with instructions to their followers on how to carry out such an attack.”

The new details came as authorities continued to explore the violent rampage that tore through a stretch of Lower Manhattan and became New York’s deadliest terrorist attack since Sept. 11, 2001.

Police say Saipov climbed into a rental truck on Tuesday afternoon and careened down a bike path along the Hudson River, slamming into numerous people before he was wounded by police and taken into custody. He drove southbound on the path “at a high rate of speed” and appeared to specifically target cyclists and pedestrians, Miller said.

Six people were pronounced dead at the scene and two more at area hospitals. Among the dead were five Argentines gathered for a reunion and one Belgian, while the two Americans were from New York City and New Jersey.

The victims of the rampage included seven men and one woman; they ranged in ages from 23 to 48. Twelve more people were injured, some critically, during the carnage. Nine of the injured remained hospitalized on Wednesday, according to Daniel A. Nigro, the New York fire commissioner.

Police on Wednesday offered their first timeline of the attack. Saipov rented a large Home Depot truck in New Jersey at 2:06 p.m. on Tuesday, they said. Using license plate readers and cameras, police tracked his travels into Manhattan and onto the West Side Highway.

He drove onto the bike path at 3:04 p.m., police said. The rampage down the path continued until he collided with a school bus, injuring still more people, at which point he emerged from the truck, according to the police narrative. A stream of 911 calls soon came in reporting the injuries, the bus accident and a man with a gun in the street.

Officer Ryan Nash, at a nearby school for an unrelated call, approached Saipov and shot him in the abdomen. The weapons Saipov were brandishing turned out to be a pellet gun and a paintball gun, police said. Officials praised Nash for his heroism in stopping Saipov, with Mayor Bill de Blasio (D) calling his actions “extraordinary.”

[ How the attack unfolded ]

The violent route, which remained a crime scene on Wednesday, was strewn with bodies, wreckage and scattered personal items such as purses, backpacks and shoes, resembling the scenes witnessed in Berlin, London, Barcelona and other places where vehicles have been used for attacks.

Investigators have spoken to Saipov, who remained hospitalized Wednesday, but officials declined to publicly reveal what he said. They also continued to scour his background and life for clues, an effort that included carrying out search warrants and interviewing people who knew him.

Saipov, a legal permanent resident of the United States, came to the country in March 2010 and had lived in Florida, Ohio and New Jersey, according to authorities. He had been an Uber driver without any worrisome safety reports, the app said, and was banned after the attack.

He had never been the subject of an FBI investigation or a New York police intelligence investigation, Miller said. However, Saipov had been known to authorities. According to a law enforcement official familiar with the current investigation, Saipov’s name surfaced during an earlier Homeland Security probe into some of his friends.

[ New York attack suspect puts focus on Central Asia’s battle with extremism ]

Video from the scene of the attack appeared to capture Saipov jumping out of the wrecked vehicle brandishing what appeared to be handguns. Some witnesses said he shouted “Allahu akbar,’’ meaning “God is great’’ in Arabic.

The Islamic State did not immediately claim responsibility for the New York attack, though its supporters cheered what happened, according to the SITE Intelligence Group, which monitors extremist activity. The militant group frequently takes credit for attacks, doing so in some cases where there is little clear indication of its involvement.

The attack may inflame the political debate over immigration and security. President Trump called Saipov an “animal” and said he was considering sending him to Guantanamo Bay.

During remarks Wednesday, Trump called the criminal justice system’s handling of suspects “a joke” and suggested it was too slow and weak, remarks he made just weeks after federal prosecutors secured the conviction of a New Jersey man who last year planted bombs in Manhattan during another attack.

On Wednesday, Trump tweeted critically about Sen. Charles E. Schumer (D-N.Y.), saying that Saipov had entered the country through a diversity visa lottery program he blamed on the senator. Trump pledged to get rid of that program, seizing on it and Schumer as political targets.

After Trump repeatedly criticized the visa program, a Department of Homeland Security spokesman confirmed Saipov came to the United States with a diversity immigrant visa.

Trump has argued for stricter screening of immigrants, which he said is needed to prevent terrorism, while opponents of his policies have repeatedly gone to court to block his efforts. Uzbekistan was not among the countries named in any version of the president’s travel ban, which largely targeted a number of majority-Muslim countries and would not have kept out anyone behind deadly terrorist attacks in the United States.

[ Experts see potential shift toward cruder, deadlier acts of terror ]

Cuomo and de Blasio said Wednesday morning that Trump had not called either of them. The men said they were not bothered because two senior Trump administration officials called them, but they also both expressed umbrage at what they described as attempts to politicize the attack.

“The president’s tweets I think were not helpful,” Cuomo said at the briefing Wednesday. “I don’t think they were factual. I think they tended to point fingers and politicize the situation.”

In the aftermath of the attack, throngs of New Yorkers went out to celebrate Halloween, with many attending the city’s annual parade, which officials extolled as a show of the city’s resilience. Police also said New Yorkers would see a beefed-up law enforcement presence in the coming days.

Cuomo, who described the truck attack as a “failed” effort to scare and terrorize people, reiterated that he felt like responses such as Trump’s were not the right way to react.

“You play into the hands of the terrorists to the extent you disrupt and divide and frighten people in this society,” he said.

As the sun rose over New York on Wednesday, the bike path remained blocked off by police tape between Houston and Chambers streets. Dozens of police officers guarded the perimeter while crime scene investigators wearing white suits slowly searched the length of the path.

At the bike path in New york, two men holding coffee cups approached the line police tape early Wednesday.

“I don’t see what happened,” one said.

“You don’t know what happened? Yesterday. Someone drive a truck into people,” the other said.

“Did people die?”

“Yeah,” said the man. “People died.”

Barrett and Berman reported from Washington. Sarah Kaplan and Monica Hesse in New York and Brian Murphy, Julie Tate and Jennifer Jenkins in Washington contributed to this report. 

White House Chief of Staff John F. Kelly was the guest for the premiere of Laura Ingraham’s new show on Fox News Channel on Monday night. During the interview, he outlined a view of the history of the Civil War that historians described as “strange,” “highly provocative,” “dangerous” and “kind of depressing.”

Kelly was asked about the decision of a church in Alexandria, Va., to remove plaques honoring George Washington and Robert E. Lee.

“I would tell you that Robert E. Lee was an honorable man,” Kelly said. “He was a man that gave up his country to fight for his state, which 150 years ago was more important than country. It was always loyalty to state first back in those days. Now it’s different today. But the lack of an ability to compromise led to the Civil War, and men and women of good faith on both sides made their stand where their conscience had them make their stand.”

“That statement could have been given by [former Confederate general] Jubal Early in 1880,” said Stephanie McCurry, a history professor at Columbia University and author of “Confederate Reckoning: Politics and Power in the Civil War South.”

“What’s so strange about this statement is how closely it tracks or resembles the view of the Civil War that the South had finally got the nation to embrace by the early 20th century,” she said. “It’s the Jim Crow version of the causes of the Civil War. I mean, it tracks all of the major talking points of this pro-Confederate view of the Civil War.”

[Kelly calls Robert E. Lee an ‘honorable man’ and says ‘lack of compromise’ caused the Civil War]

Kelly makes several points. That Lee was honorable. That fighting for state was more important than fighting for country. That a lack of compromise led to the war. That good people on both sides were fighting for conscientious reasons. Both McCurry and David Blight, a history professor at Yale University and author of “Race and Reunion: The Civil War in American Memory,” broadly reject all of these arguments.

“This is profound ignorance, that’s what one has to say first, at least of pretty basic things about the American historical narrative,” Blight said. “I mean, it’s one thing to hear it from Trump, who, let’s be honest, just really doesn’t know any history and has demonstrated it over and over and over. But General Kelly has a long history in the American military.”

Blight described Kelly’s argument in similar terms as McCurry — an “old reconciliationist narrative” about the Civil War that, in the past half a century or so has “just been exploded” by historical research since.

The idea that compromise might have been possible was rejected out of hand by McCurry and Blight.

“It was not about slavery, it was about honorable men fighting for honorable causes?” McCurry said. “Well, what was the cause? . . . In 1861, they were very clear on what the causes of the war were. The reason there was no compromise possible was that people in the country could not agree over the wisdom of the continued and expanding enslavement of millions of African Americans.”

There were a number of compromises on slavery that led up to the Civil War, from the drafting of the Constitution to the addition of new states to the Union.

“Any serious person who knows anything about this,” Blight said, “can look at the late 1850s and then the secession crisis and know that they tried all kinds of compromise measures during the secession winter, and nothing worked. Nothing was viable.”

“All of these compromises were about creating a division where slavery already existed and where for a time they conceded that the Constitution shackled them in their ability to attack it,” McCurry said. Before the war, the strategy for dealing with slavery was to contain it. By 1860, she said, the North’s economic success and expanding population and the South’s loss of representation in national politics put slavery at risk. The election of Abraham Lincoln in 1860 allowed Southern slaveholders — who had $4 billion in wealth in the form of enslaved people, McCurry said — to argue that the threat to slavery was imminent.

“In 1861, compromise wasn’t possible because some Southerners just wanted out. They wanted a separate nation where they could protect slavery into the indefinite future,” McCurry said. “That’s what they said when they seceded. That’s what they said in their constitution when they wrote one.”

Kelly’s framework is “also rooted, frankly, in a Lost Cause mentality that swept over American culture in the wake of the war, swept over Northerners,” Blight said, “this idea that good and honorable men of the South were pushed aside and exploited by the ‘fanatical’ — ironically — first Republican Party.”

Blight noted that Lee wasn’t simply defending his home state of Virginia against Northern aggression.

“Of course we yearn for compromise, we yearn for civility, we yearn for some common ground,” he added. “But, look, Robert E. Lee was not a compromiser. He chose treason.”

“The best of the Lee biographies show that Lee was a Confederate nationalist,” Blight said. “He knew what he was fighting for.”

Both historians, though, held particular disdain for the idea that putting state over nation was the essence of the fight.

“My God, where does he get that from?” Blight asked. “That denies the very reason to be, the essential reason for the existence of the original Republican Party, which formed in the 1850s to stop the expansion of slavery and ended up developing a political ideology that threatened the South because they really were going to cordon off slavery.”

“This idea that state came first? No, it didn’t!” he said. “The Northern people rallied around stopping secession! This comment is so patently wrong.”

“It’s one thing to say Lee chose state over country,” McCurry said. “What [Kelly] says is that was his country. That would be news to 350,000 Union war dead.”

“It’s just so absurd,” Blight said. “It’s just so sad. It’s just so disappointing that generations of history have been written to explode all of this and yet millions of people — serious people; experienced, serious people and now people with tremendous power — have grown up believing all this.”

There was, however, a small silver lining.

“This Trump-era ignorance and misuse of history is forcing historians — and I think this is a good thing — to use words like ‘truth’ and ‘right or wrong,’ ” Blight said. “In the academy we get very caught up in relativism and whether we can be objective and so on, and that’s a real argument.”

“But there are some things that are just not true,” he said. “And we’ve got to point that out.”

Read more: 

The truth about Confederate Gen. Robert E. Lee: He wasn’t very good at his job

Historic Alexandria church decides to remove plaques honoring Washington, Lee

How statues of Robert E. Lee and other Confederates got into the U.S. Capitol