A defining quality of Harold F. Tiernan, a retired banking executive, was his perseverance in the face of adversity, his sister recalled Monday, including the devastating quickness of the illness that took his life on Sunday. He was 66 years old.

Tiernan died of pneumonia at NewYork-Presbyterian Hospital/Weill Cornell Medical Center in Manhattan following a hepatitis C diagnosis in January. The illness, which can lie dormant in the body for decades, progressed quickly, said his sister, Audrey Tiernan, of Roslyn Heights, a Newsday staff photographer.

The six units of blood that saved her brother's life after he was stabbed in 1991 "ultimately killed" him, Audrey Tiernan said, noting the transfusions occurred before there was widespread screening of blood for hepatitis C.

In the months the illness took its toll -- with his liver and kidneys failing -- Audrey Tiernan said she learned an important lesson from her brother: "In the end, I learned how to face death with courage and grace."

Harold Francis Tiernan Jr. was born in Kew Gardens, Queens. When he was 6 years old, his parents moved the family to Garden City, where he entered the public schools, graduating from Garden City High School.

His sister said her brother had to "grow up fast" after their father, a merchant mariner, died in Vietnam in 1967. Her brother was just 19 years old then.

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"He had a lot of responsibility as a young man. He was very thoughtful, in that he didn't do anything impulsively. . . . He always tried to do the right thing. He was a good man, a great brother and terrific father. . . . He was a good guy, and he died way too soon."

His only child, Geoffrey Tiernan of Manhattan, agreed. "He was a good man, loving father. He gave great advice."

Harold Tiernan earned a bachelor's degree in business administration from Adelphi University in 1970. He then began his ascent in corporate America.

He started working at Metropolitan Life Insurance as a corporate lease analyst, his sister said. He then entered the banking industry, ultimately working at Bank of New York, where he became vice president of corporate real estate before retiring in 2012.

He was an American history and World War II buff who "was full of interesting facts," his son said.

Audrey Tiernan said her brother had a "photographic memory" and at family gatherings "would go on and on about the battle of North Africa or the battle of this."

She said her brother, who lived in Manhattan, had hoped to do volunteer work at the New York Public Library in retirement but his illness intervened.

Harold Tiernan was divorced. He is survived by his son and his sister.

Visiting is to be held Tuesday, from 2 to 4 p.m. and 7 to 9 p.m. at Fairchild Sons Funeral Home in Garden City. The funeral service is scheduled for 11 a.m. Wednesday at the Cathedral of the Incarnation in Garden City. Burial is to follow at Flushing Cemetery in Flushing, Queens. He is to be buried next to his mother, Frances E. Tiernan, who died in 2011, at age 93.

In lieu of flowers, donations may be made to the American Liver Foundation.