WARNING: This story contains details graphic details.

NEW HARTFORD, N.Y. -- A mother and father whipped their 19-year-old son in church with an electrical cord and what appeared to be a belt during a deadly, all-night spiritual counselling session triggered by his desire to leave the fold, according to witness testimony and police Friday.

Church deacon Daniel Irwin testified he peered through a doorway window in the sanctuary during the more than 12-hour ordeal at the Word of Life Christian Church and saw Lucas Leonard bleeding and in apparent agony.

"Lucas was rolling himself back and forth on the floor and making a sustained, monotone moaning," Irwin said.

Within hours, the young man would be dead, killed by blows inflicted by his parents, sister and fellow church members, authorities said. His mother told police the group took turns hitting him and holding him down, state police investigator Jason Nellis testified.

The testimony came at a court hearing for the parents, Bruce and Deborah Leonard, on manslaughter charges. At the conclusion of the hearing, a judge ruled there was sufficient evidence to sustain the charges.

The arrests in New Hartford, an upstate town of 22,000 people, have thrown a spotlight on Word of Life, a highly regimented and insular church that operated out of a large, red-brick former school that also served as a communal home for several members.

Police Chief Michael Inserra said outside court that members told authorities Lucas Leonard and his 17-year-old brother, Christopher Leonard, were beaten during what began as spiritual counselling Sunday night over Lucas' desire to leave the church.

A neighbour, James Constantine, also said Lucas had talked about moving on and had mentioned he might join the Army.

Christopher was hospitalized in serious condition, but his health was improving.

Four other church members, including the victims' 33-year-old sister, Sarah Ferguson, have been charged with assault. Their hearings will be held later. All six defendants have pleaded not guilty.

Lucas Leonard's mother and father sat silently throughout the proceeding with their heads bowed, his eyes mostly closed, her long, greying hair hanging in her face.

Bruce Leonard's attorney said prosecutors hadn't proved the couple intended serious injuries to their son. Deborah Leonard's lawyer said the mother felt helpless to stop an "intervention" she didn't expect to become so harsh.

Irwin, the church deacon, testified he got a text message after services ended around 8 p.m. Sunday saying the Leonard family would be part of a counselling session with the church's pastor, Tiffanie Irwin, his sister. Irwin said he wasn't told what the session was about and didn't participate.

From the start, it was intense: Raised voices prompted Irwin to move five children who were in a room near the sanctuary to another space farther away so they wouldn't be scared.

Watching through a window around 10 p.m., Irwin said, he saw Bruce Leonard hit Lucas up to six times with what appeared to be a belt and hit Christopher. The young men winced, Irwin said, but Lucas didn't try to defend himself.

Their mother hit Lucas with a cord out of anger over "things that he had said," investigator Todd Grant testified. He didn't ask her what those things were.

Around 10 a.m. Monday, panicked church members ran up to Irwin and said they thought Lucas was dead.

Irwin said he dashed into the sanctuary to find Lucas lying motionless on the floor, with the young man's father and brother and Irwin's mother, church spiritual leader Traci Irwin, trying to resuscitate him. Lucas was taken to a hospital, where he was pronounced dead.

The defendants include Daniel Irwin's brother, Joseph Irwin. Asked after court whether Daniel Irwin or any additional relatives could face charges, Oneida County District Attorney Scott McNamara said prosecutors "are looking at everybody that's involved," later adding he anticipates more people may be charged.

The roughly 30-year-old Word of Life church once had perhaps 40 or more members but now counts closer to 20, authorities said. Traci and Tiffanie Irwin haven't been charged and haven't commented.

There are thousands of small, independent Christian churches around the country, many of them following a very strict fundamentalist theology, said David Bromley, a religion professor at Virginia Commonwealth University. Their beliefs can lead to strong resistance when a member wishes to leave, he said.

"If you get into a very conservative group where there is only one way and God's wrath is about to be unleashed on humanity and we're the faithful remnant, then leaving the group is a very serious condition, from the point of view of members," Bromley said.

Associated Press video journalist Ted Shaffrey and writers Mary Esch and Jennifer Peltz contributed to this report.