PERRIS, Calif. (Reuters) - Police said on Tuesday they were still seeking answers after finding 13 siblings starving in their parents’ squalid Southern California home, some of them chained to beds under “horrific” conditions in an otherwise ordinary suburb.

The grim situation was discovered on Sunday after an emaciated 17-year-old girl escaped through a window of the home in a newer subdivision of Perris, about 70 miles (113 km) east of Los Angeles, and called 911, police said.

“I wish I could come to you today with information that would explain why this happened,” said Captain Greg Fellows of the Riverside County Sheriff’s Department. “But we do need to acknowledge the courage of the young girl who escaped from that residence to bring attention so they could get the help they so needed.”

The parents, 57-year-old David Allen Turpin and Louise Anna Turpin, 49, were arrested at their darkened, foul-smelling house after the girl’s 12 siblings were found there.

The shocking case quickly prompted questions of how the victims, who ranged in age from 2 to 29 years old, could have been kept in such grim conditions without raising suspicions of neighbors or authorities.

But some experts said it may have been easier for the parents to shield their children from scrutiny because they were home-schooled.

“One of the things that was interesting was, he (Turpin) set up his own home school so the kids were accounted for and not really seen by anybody,” said Sherryll Kraizer, a child-abuse prevention expert and the founder of the Coalition for Children.

The California Department of Education lists the Turpin address, where the family has lived since 2014, as the location of the Sandcastle Day School, with David Turpin as principal.

Six of the couple’s children are minors, while the rest are over 18, according to neighbors, meaning they are adults under the law.

David and Louise Turpin were each charged with nine counts of torture and 10 counts of child endangerment. They were being held on $9 million bail, with an initial court hearing scheduled for Thursday.

‘I WOULD CALL THAT TORTURE’

Police who responded to the girl’s 911 call saw that the children were malnourished, Fellows said, calling conditions “horrific.” Even so, he said, the mother appeared perplexed about why the police were there.

“If you can imagine being 17 years old and appearing to be a 10-year-old, being chained to a bed, being malnourished, and injuries associated with that,” Fellows said. “I would call that torture.”

Authorities quickly began seeking court authorization to take custody of the children. The state Child Protective Services agency was assisting in an investigation.

Kimberly Milligan, 50, said she only saw the infant in the mother’s arms and three other children since she moved in across the street two years ago, describing them as small and pale.

“Why don’t we ever see the kids?” Milligan said she asked herself. “In hindsight, we would have never thought this. But there were red flags. You never don’t hear or see nine kids.”

Two years ago, while walking around the neighborhood admiring Christmas lights, Milligan said she had encountered three of the Turpin children and complimented them on the manger with a baby Jesus set up outside the house. She said the children froze, as if by doing so they could become invisible.

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“Twenty-year-olds never act like that,” she said. “They didn’t want to have a social conversation.”

Nicole Gooding, 35, who has lived in the neighborhood for three years, said the first time she saw the family was two months ago when the mother and children were cleaning up their yard, which was full of weeds and overflowing trash cans.

“I had never seen them at all until that day,” she said.

The parents home-schooled the children strictly and required them to memorize long passages from the Bible, David Turpin’s parents, James and Betty Turpin of West Virginia, told ABC News.

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In 2010, David Turpin left his job at Lockheed Martin Corp, a company spokeswoman said. He also worked as an engineer at Northrop Grumman Corp. Both are aeronautics and defense companies.

Unable to keep up with the family’s expenses, Turpin filed for bankruptcy in 2011, an attorney who represented him, Ivan Trahan, told Reuters on Tuesday.

At the time, the lawyer said, the couple spoke highly of their children.

A Northrop spokesman declined to say whether Turpin was still employed there but said the company was “deeply troubled” by the nature of the allegations.

David and Louise Turpin appeared to have had marriage-renewal ceremonies at least three times, in 2011, 2013 and 2015, at an Elvis Presley-themed chapel in Las Vegas, according to the chapel’s YouTube page.

A video showed 10 female children in matching purple plaid dresses walking down the aisle ahead of Louise toward David, who waited anxiously at the altar with two male children in suits.

An Elvis Chapel representative did not respond to a request for comment.

A joint Facebook page that appeared to have been created by the parents showed the couple at the same chapel dressed in wedding clothes, surrounded by the 13 children.