Pivarunas was born to his father, Walter Pivarunas and an ethnic Italian mother in Chicago, Illinois. He has three brothers and a sister. He entered the religious life in September 1974, entering the Congregation of Mary Immaculate Queen taking the religious name Brother Mary Tarcisius. He made his final profession on September 12, 1980, at CMRI's headquarters at Mount Saint Michael in Spokane, Washington. In May 1984, Pivarunas was among the clergy who removed Bishop Francis Schuckardt, founder of the CMRI, under controversial circumstances. On April 23, 1985, after some time without a clear leader, Pivarunas and the clergy met with Bishop George Musey (an independent, Thuc line bishop), who agreed to advance Pivarunas and two others to the priesthood on June 27, 1985. Bishop Musey's conn