A controversial reclusive church in New York was transformed into a virtual torture chamber by some members of its own congregation recently, resulting in the brutal beating of two teenage brothers, one of whom later died from his injuries.

The incident happened during at the Word of Life Christian Church in New Hartford, a town located about 250 miles north of New York City. A small group of adults had gathered for the so-called "intervention" to allegedly force the two teens to confess their sins and seek forgiveness.  

Police have arrested six people, including the boys' parents Bruce and Deborah, and their sister Sarah Ferguson, in connection with the killing, with the father's attorney telling media that the "intervention" had nothing to do with the church and had come about from a private family meeting.

NBC New York reported that the two brothers — Lucas Leonard, 19, and his 17-year-old brother, Christopher — received multiple fist blows to their abdomen, genitals, back and thighs.

It later emerged that the hours-long mauling was carried out by the two boys' own parents — Bruce, 65, and Deborah Leonard, 59 — their sister Sarah Ferguson, 33, and a few other members of their small, tightly-knit congregation. Although a lawyer for Deborah Leonard claimed that she felt helpless to stop the "intervention" which spiralled into the physical abuse.

The police believe the group beat the two boys after they were forced to confess their sins and ask for forgiveness.

As a result of the blows he received, Lucas stopped breathing, and relatives took him early on Monday to a hospital, where he eventually died, police said.

The police then went to the church to investigate, only to find Lucas' younger brother Christopher also in a serious condition - a result of the beating.

Christopher was rushed to the hospital, where he was found to have suffered blunt force trauma injuries, police said.

"Both brothers were subjected to physical punishment over the course of several hours, in hopes that each would confess to prior sins and ask for forgiveness," Police Chief Michael Inserra said.

He said they were still trying to find out what were the two boys' supposed sins that appeared to have enraged the group.

The victim's parents have both been charged with first-degree manslaughter while four other members of the congregation, including the victim's sister, were charged with assault. The Leonards were each ordered held on $100,000 bail at their arraignment on Wednesday. Four other church members were charged with second-degree assault. All the suspects pleaded not guilty.

Inserra said at this stage of the police investigation, authorities are not alleging that the Leonard couple intended to kill their son. "But they were attempting to seriously hurt their son, and he died as a result," the police officer pointed out.

After Lucas was brought to the hospital, Inserra said they tried to look for his brother Christopher, who they suspected was also beaten. But the boys' parents and other relatives refused to tell the police where he was, Inserra said.

Finally, they were able to locate Christopher on the church's second floor after searching for hours, the police officer added.

In the village where the Leonard family lives, neighbours told police the highly religious family kept mostly to themselves.

"I'm really afraid. In my heart I don't think this is the first incident," said Eva Monaghan, who lives near the Leonards. "Over all the years, I can't imagine this is the first thing. Maybe nothing as bad. Around town, it's considered a cult."

Nancy Kneller, who used to work at a nearby Catholic church, said they have long been suspicious of the family and their secretive church.

"Why are they so secretive? Why are there no kids out playing?" she said. "I think they're good people that made a bad decision," she added.

Another neighbor, Nicole Howard, has claimed that the brothers "weren't allowed to do normal things, but they tried to be as normal as they could be."