When Sam Citrin came home from work on Tuesday afternoon, he saw police officers blocking streets near his house and heard helicopters hovering overhead. He walked a little bit toward the Hudson River, then turned around. His mind had begun to replay memories of Sept. 11, 2001, and he wanted it to stop.

"It was a bit of an unwanted reminder of that day, to be honest," said Mr. Citrin, 50. "It just opened that wound, you know?"

On that day 16 years ago, the native New Yorker had been walking his two dogs early in the morning when he saw the first plane hit the World Trade Center. On Tuesday, he had planned to take his daily bike ride, an hour-long trip to the George Washington Bridge and back along a path that traces the west side of Manhattan. Instead, he met a friend for dinner at an Italian restaurant.

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Eight people were killed and 11 seriously injured on Tuesday after a truck driver plowed down people on a riverfront bike path near the World Trade Center, brandishing air guns and yelling "God is great" in Arabic. The driver — identified by officials as an immigrant from Uzbekistan — was in critical condition but expected to survive after a police officer shot him in the abdomen.

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Later in the evening, Mr. Citrin sat on a bench outside the Ear Inn, a bar a block away from the site of the attack, and contemplated the twists of fate that kept him off his bike that afternoon. Tuesday's deadly violence fulfilled a grim prediction: "I've been saying for years, it's not a matter of 'if,' it's a matter of 'when'" another attack is going to happen, he said. "And today it happened."

If some New Yorkers had been dreading this day, they did not outwardly show it. The annual Halloween parade went on as scheduled, hours after the worst terrorist attack to hit the city since September, 2001. A stretch of the West Side Highway – still an active crime scene – remained closed, but there were bicyclists and dog-walkers on a different section of the same path where eight people had been killed hours earlier.

Gary Lawler, the manager of the Ear Inn, remembered how he kept the bar open for 48 hours after the Sept. 11 attacks to provide a place for people to gather and grieve and search for loved ones. "This is where people come when things go pear-shaped," he said. "Then we recoup and figure out what to do next."

On Tuesday night, a television in the bar was showing the World Series and the room was loud. Among the regulars, there was an undercurrent of anxiety: With the names of the victims still not released, they wondered if the list might include someone they knew. Mr. Lawler said the bar would keep its normal hours, closing at 4 a.m. as it does every day. "You can't keep New Yorkers down," he said. "They will not break us."

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Next door, a tapas restaurant was having its regular twice-monthly event for aficionados of Kizomba, a style of African dance. Earlier in the evening, the organizers held a minute of silence for victims of the attack. Femmel De La Rosa, 24, and Jerell Johnson, 31, said the violence did not alter their plans to head downtown. "I've lived here my whole life," said Mr. Johnson. "We shouldn't change what we do."

Other groups of young New Yorkers headed home in costume after attending the Halloween parade in Greenwich Village, where they were joined by Bill de Blasio, the city's mayor, and Andrew Cuomo, the governor of New York State. "You have to live your life," said Amar Maraj, 18, who was dressed as a go-go dancer. But the parade was less exuberant than in past years, he said.

Overhead, a constant thrum of helicopters reminded New Yorkers of the rip in the fabric of their city. Along the road where the attack took place, technicians in white jumpsuits scoured the asphalt for evidence, walking in rows and holding flashlights. Otherwise, the normal routine prevailed. A waiter carried in tables from the patio of the Tribeca Grill. A row of black sedans sat in front of the headquarters of Goldman Sachs, waiting to take staff home after late nights at the office.

Three blocks south of the spot where the rampaging truck came to a halt, at the place where the World Trade Center once stood, all was quiet. A yellow plastic chain indicated that the area was closed until morning, when it would reopen at 7:30 a.m. Two workers were performing the daily task of polishing and sanding the panels of the memorial where the names of the dead are inscribed.

Jesse James, a security guard standing nearby, looked affronted when asked if Tuesday's attack would change his behaviour. "No – for what?" he responded. He grew up in some of the city's roughest neighbourhoods, Mr. James said. "If you walk around scared all day, you'll never leave your house."

With a file from the Associated Press