McGee was born in Ireland and came to the United States at age 17. He vociferously promoted the cause of Irish revolution in America, including publishing in the pages of Boston's Catholic newspaper, The Pilot. After a time of revolutionary activity in Ireland, he returned to the U.S., where his views provoked controversy with Bishop John Hughes of New York. He settled in Montreal, where he entered the Parliament and his political views changed entirely; now he supported British supremacy in Ireland. His switch raised the ire of his erstwhile allies, one of whom murdered him in the Canadian capital.