CLAYVILLE, N.Y. — The pastor of a secretive church in central New York was holding a meeting to address concerns that a teenage congregant wanted to defect when other church members began to beat the teenager in an attack that eventually stretched over 10 hours, a prosecutor said on Thursday.

The congregant, Lucas Leonard, 19, later died, and his younger brother, Christopher Leonard, 17, remained hospitalized on Thursday with serious injuries inflicted during the beating, which, the authorities said, started after Sunday services and lasted until early on Monday. The teenagers’ parents were charged with manslaughter in the death, and a half sister was charged with assault.

A police spokesman said counseling sessions like the one that preceded Lucas Leonard’s death were a routine practice at Word of Life Christian Church, in the town of New Hartford, N.Y., and were meant to deal with questions about adherents’ spiritual standing. But the spokesman said investigators had no indication that the sessions had led to beatings before.

Defense lawyers for the teenagers’ parents, Bruce T. Leonard, 65, and Deborah Leonard, 59, offered a sharply different account of the meeting, describing it as a family gathering to discuss the teenagers’ behavior toward relatives and church members. A lawyer for Ms. Leonard, Devin Garramone, said, “It had something to do with the boys maybe touching some of the other children in the church.”