Mark Pivarunas entered the religious life in September 1974 entering the Congregation of Mary Immaculate Queen taking the religious name Mary Tarcisius. On June 27, 1985, Brother Mary Tarcisius was ordained priest.
Father Mary Tarcisius served as the rector of the Congregation’s seminary for four years. In August of 1989, at the age of 30, he was elected Superior General of the Congregation of Mary Immaculate Queen.
On September 24, 1991, Father Pivarunas was consecrated bishop by Bishop Moises Carmona in Spokane, Washington.
On November 30, 1993, Bishop Pivarunas consecrated bishop the Reverend Daniel Dolan in Cincinnati, Ohio.
Bishop Pivarunas resides in Omaha, Nebraska serving as Superior General of the Congregation of Mary Immaculate Queen and as rector of the Congregation's seminary there.