“It was a nerve-racking moment,” said Dick Lehr, a Spotlight reporter who worked on the series with Mr. O’Neill. But he and Mr. O’Neill both had sources within the F.B.I. who confirmed that Mr. Bulger was an informant — a fact that the F.B.I. and the Justice Department took 10 years to acknowledge publicly.
Mr. O’Neill and Mr. Lehr would go on to write three books together, including two about Mr. Bulger: “Black Mass: The Irish Mob, the FBI, and a Devil’s Deal” (2000), which was made into a 2015 movie starring Johnny Depp as Bulger, and “Whitey: The Life of America’s Most Notorious Mob Boss” (2013).
Through their years of collaboration, Mr. Lehr said, Mr. O’Neill was calm and steady.
“When you confirm something important, it’s exciting, but he knew not to get too high or too low because these things take a long time,” he said. “That was a good way to learn how to manage these in-depth projects.”
Gerard Michael O’Neill was born on Sept. 1, 1942, in Boston to Richard and Mary Claire (Sweeney) O’Neill. The family soon moved to Stoughton, a Boston suburb, where his father became a postal inspector and his mother worked as an operating-room nurse.
Mr. O’Neill graduated from Stoughton High School and attended Stonehill College in Easton, Mass., graduating in 1964 with a degree in English. While there, he met Janet Reardon, a fellow student, whom he married in 1968.
In addition to his son Shane, she survives him, as does another son, Brian; his sister, Maureen Dennis; and two grandchildren.
After college, Mr. O’Neill briefly attended George Washington University Law School in Washington. But he was not happy there and returned to Boston, where he got a job as a copy boy at The Globe and earned a master’s degree in journalism from Boston University in 1970.
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