O'Callaghan studied at the Collège de Montréal, a Sulpician school in Canada, for six years and then enrolled at the College of the Holy Cross in Massachusetts.
[4][3] On September 4, 1863, O'Callaghan became the rector of St. Stanislaus novitiate in Frederick and became the master of novices of the Jesuit Province of Maryland, where he succeeded James A.
[1][8] On January 21, while sailing across the Atlantic Ocean, back to the United States,[2] a large wave struck his ship.
The wave broke the walls of the cabin and threw a heavy table on top of O'Callaghan's chest, killing him almost instantly.
[10] While in Rome, O'Callaghan had been given papers appointing him the provincial superior of the Maryland Province, which he was carrying aboard the ship when he died.