John J. Cassidy died on January 21, 2015. He was a battalion chief with FDNY Battalion 40. He died from cancer related to the recovery efforts at the World Trade Center after September 11, 2001.

John was a U.S. Army veteran.

He was the beloved husband of Mary Cassidy; loving father of John (Michaela) and Michael; devoted grandfather of John and Katherine; treasured uncle of many nieces and nephews; dear brother-in-law of Jane Slater, Michele Reilly, Helen Maloney, Denise O’Rourke, William Maloney, and Jeremiah Maloney; and adored cousin of Mary Ann Garoklanian, Donna Farrell, Janice Garoklanian, Charles Garoklanian, and Donald Welsh.