Stepping into the dojo, Alexander Capelluto ’08 brought the same spirit to karate that he brought to everything else in his life.

He was an experienced martial artist, but never shied away from drilling exercises with younger karate students. This was how Capelluto’s family and friends said they remember him — always willing to teach and to inspire.

Capelluto, who was killed in a biking accident on Thursday, was described by those who knew him as a fun-loving and outgoing instructor, student and friend — an energetic young man whose dedication and often consuming zeal spilled over into those around him, whether he was organizing Hurricane Katrina relief efforts or gearing up for a nation-spanning Habitat for Humanity bike challenge.

“He ‘got’ everyone he met; he understood them and helped them understand each other,” Capelluto’s sister, Katherine Capelluto ’04, said in an e-mail. “Losing Alexander leaves a hole in all our lives.”

Born and raised in New York City, Alexander Capelluto attended the Horace Mann School before matriculating at Yale. During his high school years, classmate Logan Lowe said Capelluto consistently worked to make sure that everyone in their 10th grade geometry class learned the material.

“He made you want to spend time with him, made you want to do work with him,” he said. “He really would make you excited and make you feel like … you were on the right track.”

The valedictorian of his class, Capelluto also served for four years as its president. At Yale, he participated in Freshman Outdoor Orientation Trips and walked onto the lightweight crew team this past year. Teammate Ben Elkins ’08 said Capelluto made a concerted effort to mesh with the team from the beginning, but was not afraid to take initiative, either, organizing a fundraising event for Hurricane Katrina relief in the fall.

“He worked to make it a team fundraiser,” Elkins said. “It was certainly something he didn’t think he could do, but he did it.”

Capelluto’s friends and family said his commitment to others always came before his own needs. High school classmate and friend Devin Balkind said that while he vividly recalls his and Capelluto’s shared passion for James Bond movies, the most memorable aspect of his classmate was his empathy.

“Aside from being more or less a genius … he was just an inspiring kid,” Balkind said. “When all of us were complaining about the 80 hours of community service we had to do, he was on hour 130.”

Priya Prasad ’08, who lived above Capelluto during their freshman year, remembers him as a “brilliant” student who worked to support those in need of academic help rather than flaunting his intelligence.

“Everyone came by his room,” she said. “The door was always open.”

Those close to Capelluto said that he touched the lives of everyone around him, whether hiking through the Berkshires, rowing for all he was worth, or just sitting out on the deck with his guitar and some company. Longtime friend Jared Iverson, a resident of New Hampshire who met Capelluto at summer camp in Maine, said that family, friends and even casual acquaintances are traveling from throughout the nation to share memories of Capelluto at his memorial service.

The service will be held at Congregation B’nai Jeshurun in New York City on Monday at 12:30 p.m.