Education
University of Navarra.
University of Navarra.
He was ordained on June 25, 1995 and was incardinated in the diocese of Lleida. In 1998 began missionary work in Kazakhstan. He was rector of the seminary in Karaganda.
On March 5, 2011 Pope Benedict XVI appointed him bishop of the Holy Trinity in Almaty.
He replaced the retiring Bishop Henry Howańca, OFM. On May 8, 2011 Sierra was ordained bishop by Apostolic Nuncio to Kazakhstan, Archbishop Miguel Maury Buendía.