Nick Antonelli, 98, a retired Washington area homebuilder who as a boxer in his younger years recorded one of the fastest knockouts in the sports history, was found dead Nov. 21 at his home in Kensington.

Mr. Antonelli had heart ailments but was otherwise relatively healthy and lived an independent and active life, said his son Morris, a dentist from Kensington.

The Saturday before his death, Mr. Antonelli attended the annual fundraising dinner of the Greater Washington, D.C., Jewish Sports Hall of Fame, of which he was an inaugural inductee in 1995.

At the dinner, he chatted with friends and reminisced about his pugilistic exploits, first as a bantamweight fighter, then as a youth boxing coach in the Washington area.

Conversations about Mr. Antonelli's years in the ring usually drifted back to July 6, 1926, when he entered the record books by winning a match just five seconds into the first round.

He was 19 years old at the time, a lean, street-tough New Yorker, in his third year as an amateur boxer, fighting in front of a hometown crowd at the Golden City Arena in Brooklyn. At 5-feet-5, he was small in stature, but he had large, heavy hands that he utilized in a hard-charging style to amass an amateur record of 111 wins -- 90 by knockout -- and 10 losses.

But it was his fight with George Bard that earned Mr. Antonelli a place in boxing lore. At the opening bell, before spectators could become comfortable in their seats, Mr. Antonelli sent Bard flying out of the ring with a left hook to the head. Instead of climbing back through the ropes, Bard retired to the locker room. Official time of the bout: five seconds.

The Everlast Boxing Record Book listed the contest as the world's fastest knockout. The fight even became a featured item in Ripley's Believe It or Not.

About two years later, Mr. Antonelli, who had come close to winning a spot on the 1928 U.S. Olympic boxing team, moved to Washington with his family when his father took a job installing tile and marble in the Ambassador Hotel that was under construction.

At the time, though, boxing was illegal in the District, so Mr. Antonelli, who was by then fighting professionally with the ring nickname the "Li'l Fire Engine," regularly fought on boxing cards in Norfolk, Baltimore and Newport News.

He was known, too, as the Italian Jewish boxer whose trunks featured a Star of David emblazoned on the left side. For many, it was an oddity because of his Italian surname. Mr. Antonelli, who was born in New York into a traditional Italian Catholic family, converted to Judaism in 1932 after developing an affinity for the faith in Brooklyn.

Growing up, he attended bar mitzvahs of friends and seemed profoundly touched by the chants and prayers that emanated from a synagogue next to his home, his son said.

Mr. Antonelli retired from boxing in 1934 after about 150 fights as a professional. He won 144 of his bouts and was never knocked out.

Following in his father footsteps, he worked as a tile craftsman until he joined the Navy Seabees during World War II. He served mainly in the Pacific, coached the 128th Battalion boxing team and tiled a captain's shower on a ship.

After the war, he became a general contractor, building single-family homes and small garden apartments in the District and Montgomery County.

After work and on weekends, he lent his expertise in the "Sweet Science" as a volunteer boxing coach at the Jewish Community Center in the District and at the Wheaton Boys Club.

"He had something to contribute that was unique," Morris Antonelli said of his father. "Boxing is what he knew best."

His wife, Pearl Antonelli, died in 2000. They had been married for 68 years.

In addition to his son, survivors include another son, Joseph Antonelli of Washington; a daughter, Sharon Antonelli of Fort Myers, Fla.; a sister; three grandchildren; and six great-grandchildren.