Kelly was born in the Drexel Hill suburb of Philadelphia to Francis G. Kelly (1901–1966) and Rose M. (Lally) Kelly (1908–1973). His sister Kathleen was born in 1946. In 1952, the family settled in Brighton, Massachusetts and his father continued to work for Corn Products in South Boston.
In Brighton, John Kelly attended Saint Columbkille School, where he got his inspiration for a humorous story about growing up in parochial school, which was published in The Boston Globe Magazine in 1973, titled "The Sisters and the Kids".
Francis Kelly was a salesman for Corn Products, which led the family to move to Manchester, New Hampshire in 1949. After graduating Saint Columbkille School, John joined the United States. Air Force. He left Brighton for basic training at Lackland Air Force Base, on July 1, 1961, aged 17.
After basic training, he was deployed to what was then Formosa, where he started his radio career in Armed Forces Radio.
After returning to the United States he was stationed in Maryland. In 1967, the family moved to Brighton, Massachusetts, where he worked for Ross Laboratories.
In 1968, he joined WCAS (Department of Administration and Management) as a reporter and producer of documentaries. In 1970, he joined WBZ (Department of Administration and Management) News, where he significantly contributed as investigative reporter for several years, earning awards for excellence in reporting from United Press International.
Kelly joined WNAC-television in 1974 as an investigative reporter.
John Kelly died in the Blackfriars Massacre in 1978, aged 34.
