A woman walking her dog tipped off Mercer County authorities to “a human skeleton” she saw outside a house along North Second Street in Greenville.

What investigators found was a 7-year-old boy so starved of food, he was reduced to scavenging for insects, and his weight had dwindled to 20 pounds, the lead investigator told the Tribune-Review.

“He looked like a Holocaust victim,” said Mercer County Detective John J. Piatek, who specializes in child abuse cases. “He had been beaten with a belt every time he tried to get food. He had three abscessed teeth and weighed 20 pounds when he was taken to Children’s Hospital. The starvation could have killed him. The abscessed teeth could have killed him.”

The boy’s mother, Mary C. Rader, 28; maternal grandparents Dennis C. Beighley, 58, and Deana C. Beighley, 47 — who all live the North Second Street house — each have been charged with multiple counts of aggravated assault, unlawful restraint of a minor, false imprisonment, child endangerment and criminal conspiracy. The three are free after posting a $75,000 unsecured bond on Friday.

The boy’s mother Mary Rader (right), 28, and his grandmother, Deana Beighley (left), 48, are pictured outside of Pennsylvania court. The home at which the abuse occurred is inset.

Their sole motive, Piatek said, seems to have been that they disliked the child.

Dr. Jennifer Wolford of UPMC Children’s Hospital Child Advocacy Center told investigators from Mercer County Children and Youth Services that “it was the worst case of childhood starvation she had ever seen,” Piatek said.

UPMC officials told the Trib that they could not discuss an open child abuse investigation.

The boy is in foster care. His sisters — 11 and 14 — and a brother, 9, have been placed in different homes and are healthy, authorities said

The older brother was underweight “but not nearly as bad” as his sibling, who was rushed last month to Greenville’s UPMC Horizon Hospital and transferred to Children’s Hospital in Lawrenceville, Piatek said.

“I went to see him,” said paternal grandmother, Debra Rader of Mercer County. “It was horrible. I’m sorry, but you wouldn’t do to a dog what they did to that beautiful boy. They should starve them, and see if they like it.”

During a week’s stay, he gained a pound a day and has since gained 24 pounds.

Debra Rader’s son, Jimmy, is divorced from Mary Rader. Debra Rader said she twice reported her ex-daughter-in-law to Mercer County authorities.

“She acted strange all the time,” said Debra Rader, 56. “We would go over there to check on the boy, but we were never allowed to see him, so we weren’t sure what was going on.”

Piatek said that Children’s Hospital experts believe that if investigators had not saved him, the child “had one more month before he went into cardiac arrest.”

Although the boy sometimes received a chunk of tuna fish to eat, Piatek said that the adults, who all lived in the same home, would beat him if he tried to get other food, such as bread or peanut butter.

“The doctors said that the only medicine he needs now is food,” Piatek said.

No one answered calls placed by the Trib to the Beighleys’ home or knocks on their door. A message left on a phone linked to Rader was not returned, and other numbers once tied to the family are no longer in service.

No defense attorney was listed in court documents.

Except for traffic citations, none of the defendants had been charged with any previous crimes in Pennsylvania.

According to Piatek, the boy’s mother removed him from school a year ago and enrolled him in cyber classes. It did not have a live camera feed for instructors to check if the right child was online studying. Investigators do not know if the boy logged on or if others did it for him.

A preliminary hearing is scheduled for July 30 before Magisterial District Judge Brian Arthur in Greenville.

Staff writer Alex Nixon contributed to this report. Carl Prine is a staff writer for Trib Total Media. He can be reached at 412-320-7826 or cprine@tribweb.com.