Vatican City: Pope Francis appointed Auxiliary Bishop John P. Dolan of San Diego to become the leader of the Roman Catholic Diocese of Phoenix, replacing Bishop Thomas J. Olmsted. Olmstead has been the bishop of Phoenix for more than 18 years.

"My brothers and sisters in Christ, I have no doubt that you will come quickly to know our new bishop's joyful spirit and his generous heart," said Bishop Thomas J. Olmsted during a press conference introducing Dolan.

After turning 75 in January and having reached the age limit for bishops, Olmsted sent a letter to Pope Francis asking for permission to retire. After five months of discernment, Pope Francis accepted the request.

According to the Roman Catholic Diocese of Phoenix, Bishop Dolan will begin his new assignment in Phoenix in early August, taking over one of the "fastest-growing" Catholic dioceses in the United States with an estimated 1.1 million Catholic population.

Dolan grew up in the Clairemont neighborhood of San Diego as one of nine children. He was ordained a priest of the diocese in 1989. Dolan served as a priest in the Diocese of San Diego for nearly 28 years before he was appointed as auxiliary bishop.

He has served as vicar general and moderator of the curia. As vicar for clergy, he also assisted Bishop Robert McElroy in the assignment of priests in San Diego’s 98 parishes.

“I cannot begin to express my thanks to God for his goodness to me throughout my life and I enter this new chapter with a renewed commitment to love and serve the Lord and His Church with my whole heart, soul, and strength,” Bishop Dolan said in a press release.

The Phoenix bishop-elect was also known in San Diego for his support of refugees, in particular the Lost Boys of Sudan, a group of more than 20,000 boys from the Nuer and Dinka ethnic groups who were orphaned or left home during the Second Sudanese Civil War.