Gaeton Fonzi, 76, a magazine reporter who investigated the assassination of President John F. Kennedy for congressional committees in the 1970s, died Aug. 30 at his home in Satellite Beach, Fla. He had Parkinson’s disease.

His wife, Marie Fonzi, confirmed his death.

Mr. Fonzi was an investigator for the Senate Select Committee on Intelligence from 1975 to 1977 and for the House Select Committee on Assassinations for two years after that.

Mr. Fonzi came to believe that Kennedy was assassinated as a result of a conspiracy that he alleged involved the CIA. Mr. Fonzi’s research led the House committee to conclude in its official 1979 report that there was “a high probability that two gunmen” shot at Kennedy in Dallas and that the president “was probably assassinated as a result of a conspiracy” — although the committee specifically excluded the CIA, the FBI, organized crime, and the Soviet and Cuban governments from any alleged conspiracy.

Mr. Fonzi took issue with the final report, saying he had established a link between the CIA and Lee Harvey Oswald, the accused assassin of Kennedy. Mr. Fonzi published a book explaining his findings, “The Last Investigation,” in 1993.

“His whole obsession was the Kennedy assassination,” his wife said.

“He was in constant contact with everybody about that” for years, she said. “He went and spoke in Dallas almost every year” at gatherings where the assassination was discussed.

Gaetano Fonzi was born Oct. 10, 1935, in Philadelphia. (He later dropped the final letter of his first name.)

Mr. Fonzi graduated from the University of Pennsylvania in 1957, where he wrote for the campus newspaper. He was briefly a reporter at a Pennsylvania newspaper before serving as an Army infantry officer.

In 1959, he joined what became Philadelphia magazine, a publication for business executives at the time, and helped turn it into a trend-setting publication.

“He did a lot of great stuff,” recalled D. Herbert Lipson, chairman of Metrocorp, owner of Philadelphia and Boston magazines.

“In those days, we wanted to cure all the ills of the world,” Lipson said, nothing that Mr. Fonzi sometimes took years to gather evidence before publishing his investigations.

One of Mr. Fonzi’s stories, in which he collaborated with another writer, exposed a Philadelphia Inquirer reporter who collected kickbacks in return for not publishing critical stories.

The reporter, Harry Karafin, later went to prison.

Gil Spencer, the late top editor at the Philadelphia Daily News, said in 1989 that Mr. Fonzi was among the first reporters “to turn regional magazines into investigative instruments.”

In 1970, Mr. Fonzi published a biography of Walter Annenberg, a former publisher of the Philadelphia Inquirer, diplomat and philanthropist.

After leaving Philadelphia in 1972, Mr. Fonzi became an editor and part owner of Miami magazine before working for the congressional committees.

He later contributed to magazines, studied the Kennedy assassination and pursued an interest in sailing.

In addition to his wife of 55 years, survivors include four children; eight grandchildren; and two great-grandchildren.

— Philadelphia Inquirer