oh wait there was apparently a deleted scene about that
from imdb trivia: In a deleted scene, Ray and Ken are lying in their beds discussing Ray's murder of the priest and the little boy. Ray ponders over why he was sent to kill the priest, guessing it was likely pedophilia. Ken counters that Harry was behind a land-buying deal that the priest opposed. These two explanations are coincidentally two different motives that are suggested for the archbishop's murder in Primal Fear (1996).