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Dennis  M.  OCallaghan, Sr.

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Retired FBI Agent Dennis M. O’Callaghan, Sr., 59 years, of Nahant, died Thursday at home after a long illness. He is the husband of Maryanne (McDermott) (Cassidy)O’Callaghan.

He was born in Brooklyn NY, the son of the late Leo J. and Agnes (Broderick) O’Callaghan. He was raised in Great Neck, Long Island NY, and was a graduate of St. Mary’s High School, Manhassett, Long Island, NY. He was a graduate of St. Mary’s College, Maryland, Class of 1962. He attended St. John’s University Brooklyn NY. He lived in many places due to assignments including Boston, Washington DC, Philadelphia PA, Minneapolis, MN and most recently in Nahant.

He was an Air Force Veteran of the Viet Nam Conflict. He served as a Captain in the US Air Force Security Police, providing security for Air Bases throughout Viet Nam and the United States.

He is a member of the Society of Former Special Agents of the Federal Bureau of Investigation. He was the North East Bungee Jumping Champion in 1993. He also enjoyed reading.

He was a 24 years veteran of the Federal Bureau of Investigation. He was the Assistant Special Agent in Charge, Boston Division, from 1988 to 1996; Chief of the Organized Crime Unit in Washington DC from 1986 to 1988; from 1984 to 1986 he was in the Washington DC FBI Inspection Division. While in the Philadelphia Division of the FBI from 1977 to 1984, he was the Supervisor of the Organized Crime Squad. He directed a joint task force with the Philadelphia Police Department. The impact of this task force solved 13 murders and led to convictions of organized crime families. This work was also the basis for the book “Breaking the Mob”. While in Minneapolis MN he served as a FBI Investigator from 1968 to 1972.
In 1992 he was selected to serve as a consultant to the Direzione Investigativa Antimafia, a newly formed police agency in Italy investigating organized crime.

He is survived by his devoted Loving Partner and wife: Maryanne(McDermott)( Cassidy)O’Callaghan.A son and daughter-in-law: Dennis M, Jr. and Jennifer O’Callaghan of Houston TX;A daughter and son in law Stacy and Kevin Connolly of Watertown; 2 stepdaughters: Jackie Cassidy of Swampscott and Megan Cassidy of Nahant. A Brother and sister-in-Law Leo J., Jr. and Marcella O’Callaghan of So. Hampton NY;A sister and brother-in-law Sharon and Thomas Drumm of Cape Carol, FL;1 granddaughter Anna Lee O’Callaghan of Houston TX; He also leaves his Father in law and Mother in Law :Jack and Cathy (Owens) McDermott of Lynn and several nieces and nephews.

His funeral will be held on Monday at 9:00 AM from the Solimine Landergan and Richardson Funeral Home 67 Ocean Street (RT1A) Lynn, followed by a funeral Mass in St. Mary’s Church 8 South Common St., Lynn at 10:00 AM. Cremation in Harmony Grove Crematory, Salem.

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