When he decided to become a priest, he left the university to enter Holy Trinity Seminary in Irving, Texas.

He received his Bachelor of Arts in philosophy from Holy Trinity in 1978 and his Master of Divinity degree in 1982 from the University of Dallas.

He left All Saints in 1986 to become chaplain at the University of Dallas, holding that position for the next ten years.

[1][2] Pope Francis appointed Kelly as an auxiliary bishop of Dallas on December 16, 2015.

[4][1] On February 11, 2016, Kelly was consecrated at the National Shrine Cathedral of Our Lady of Guadalupe in Dallas by Bishop Kevin Farrell, with Archbishop Michael Sheehan and Bishop J. Douglas Deshotel acting as co-consecrators.