In 1871, he was one of several Irish-American veteran officers who participated in an attack (not officially sanctioned by the Fenian Brotherhood and thus not considered by all a true "Fenian raid") by a combined force of Irish-Americans and Pembina-area Métis on the Hudson's Bay Company trading post at the international border in October 1871. The Americans were captured by a unit of the American army, and released after a hearing in which it was concluded that such an attack, however imprudent, did not violate American law. The Métis were not so lucky.