People place candles during a vigil organized in front of the prestigious polytechnic high school in Rosario, Argentina on Nov. 1. (Eitan Abramovich/AFP/Getty Images)

A small wooden work stool, carved with designs and painted or branded with initials, is the first project that students must complete when entering the prestigious Instituto Politecnico Superior here. They keep the stools through six years of arduous classes and beyond — a symbol of their progress but also of the bonds they develop with their classmates.

Members of nearly every graduating class, whether from 2017 or decades past, come together at some point during the year to paint the stools again on the sidewalk outside the school, or they just bring them along during barbecues and trips together.

Now, five stools from the class of 1987 are missing their owners.

The classmates died in Tuesday's terrorist attack in New York while celebrating the 30th anniversary of their graduation from the high school known as "Poli."

Their deaths have rocked this city about 185 miles northwest of the capital, Buenos Aires, shocking a tightknit community that revolves around the elite school founded in 1906.

More than 200 people held a vigil outside the polytechnic institute on Wednesday night, spilling out onto the street as they wept and embraced. Because most friends and family members said they were too grief-stricken to leave their homes, the majority of those in attendance were teachers, students and alumni who had never met the victims.

(Cecilia Piedrabuena via AP) From left to right, Hernan Ferruchi, Alejandro Pagnucco, Ariel Erlij, Ivan Brajckovic, Juan Pablo Trevisan, Hernan Mendoza, Diego Angelini and Ariel Benvenuto gather on Saturday, Oct. 28, 2017, for a group photo before their trip to New York City, at the airport in Rosario, Argentina.

"What you realize is that if you don't have a direct contact, there is always a friend or a sibling who did," said Maximiliano ­Bosch, who graduated 10 years before the victims did. "The connections at this school are strong."

Teachers who had never taught the victims huddled together, most of them too sad to speak to reporters who had flocked to Rosario from the capital.

"I struggled to explain to my students what this loss meant," Diego Espinosa, a communication technologies teacher, managed to say. "It's a huge loss to the school. It's a huge loss for the city."

The friends who met in New York — Diego Angelini, Hernán Diego Mendoza, Ivan Brajckovic, Alejandro Damián Pagnucco, Hernán Ferruchi, Juan Pablo Trevisan, Ariel Benvenuto, Martín Ludovico Marro and Ariel Erlij — were excited about being all together in one place for the first time in years.

Members of the City Council in Rosario, Argentina, display a banner during a Nov. 2, 2017, ceremony in honor of five residents killed in a terrorist attack in New York on Oct. 31. (Marcos Brindicci/Reuters)

On the third day of their trip, the men, all in their late 40s, were riding bicycles alongside the Hudson River in Lower Manhattan when a rented pickup truck veered onto the bike path, accelerated quickly and began mowing down cyclists and pedestrians over a 20-block stretch. Five of the Argentines — Ferruchi, Pagnucco, Erlij, Mendoza and Angelini — were killed, along with three other cyclists: a Belgian woman on vacation and two American men who worked or lived nearby. At least a dozen other people were injured, including Marro, a longtime U.S. resident who joined his former classmates in New York from his home near Boston and was hospitalized with unspecified injuries.

The alleged perpetrator of the attack, Sayfullo Saipov, a 29-year-old immigrant from Uzbekistan, was shot and wounded by a police officer after he smashed the truck into a school bus. He is facing terrorism ­charges.

"When someone unjustly takes a life without any reason at all, how are you supposed to feel exactly?" said Graciela Daneo, 63, a cousin of Benvenuto, one of the survivors. "You go on a vacation and you don't expect anything to happen. You don't expect terrorism."

Saipov had allegedly planned the attack for more than a year, nearly as long as the friends from Rosario had been preparing their trip. Yet for residents of the city, the tragedy seemed more like a freak accident than a planned event — something they could not imagine happening to members of their own community.

Even within Argentina, Rosario, the nation's third-largest city, is often overshadowed by the capital and by rich, historical Cordoba, about 250 miles to the northwest. Situated in the heart of Argentina's main industrial region, Rosario is just about the country's closest equivalent to a Rust Belt city — chugging along out of the national spotlight, let alone an international one.

"It seems like a tragic fate that this happened to those five classmates," said Martin Boix, 39, a former student at Poli. "New York is an immense city with millions of hearts passing through it, and this happens to five of Rosario's."

For 111 years, the polytechnic institute has been a source of pride for Rosario, producing some of the country's most prominent engineers, architects and politicians — including Miguel Lifschitz, governor of Santa Fe, the province where Rosario is located.

As many as 1,000 students apply to the school each year through an entrance exam, and only 230 are admitted. They are often expected to work up to 10 or 12 hours a day and to stay for a year longer than other high school students in Argentina. The time and effort they put in leave each graduating class feeling like a brotherhood, many students said.

At Wednesday night's vigil, Arnando Amillone, who graduated in 1953, lit a candle in front of the school and stood watching it burn for nearly a half-hour. Alumni who had graduated decades after him, even as recently as last year, began setting their candles beside Amillone's.

Because many students leave the institute with lifetime friendships, some of them said the tragedy in New York has made them look inward, at their own relationships and celebrations.

Gonzalo Ibañez, who graduated a year after the five victims, said he and his friends from Poli were planning a trip to celebrate the 30th anniversary of their graduation. Even though the tragedy could have happened to any group of friends from the school, he said, it will not stop them from getting together, nor from celebrating next year.

And when they do, he said, he will bring along his stool.