O'Neill died Monday of esophageal cancer at South Shore Hospital in Weymouth, a hospital spokesman said. He served as a firefighter on Ladder 17 in the Back Bay for 35 years, until he retired in 1985.
On July 22, 1975, O'Neill was at a six-story Back Bay building that was engulfed in flames. Diana Bryant, 19, and her goddaughter, Tiare Jones, 2, were trapped on the fifth-floor fire escape.
He climbed down from the roof to try to save them, but seconds before the three could climb onto a rescue ladder, the fire escape gave way, sending Bryant and Jones plummeting to the ground. O'Neill hung by his arm from the ladder.
Bryant died, but her goddaughter survived.
A picture of Bryant and Jones in freefall taken by Boston Herald American photographer Stanley J. Forman won the 1976 Pulitzer Prize in journalism for feature photography.
''There was no warning. I didn't think there was any reason to worry. It appeared to be a routine rescue,'' O'Neill told the newspaper, now the Boston Herald. ''I had them, I was right there ... just two more seconds.''
O'Neill, a widower, is survived by two sons, a daughter, two brothers, three sisters and eight grandchildren.
