For months, Sharon Glass locked a boy inside a tiny bathroom with a boarded-up window. The boy starved and slept on the bare floor. The photographs presented in the Florida courtroom were gut-wrenching, resembling something out of a concentration camp.

The victim, nearly 13 years old, weighed just 40 pounds. His clothes, made for an 8-year-old, sagged off his tiny body. Prosecutors said that if the abuse and starvation had continued for another month, the boy would have been dead.

“I can state during the 15 or so years I’ve been here I’ve probably had two or three cases I would consider the conduct just pure evil,” Judge David Dugan said during the trial. “This was cold. This was calculating. This was evil.”

It was also a case that Florida’s Department of Children and Families knew about. In fact, DCF had been warned about the boy for years.

Glass’ ex-husband reportedly called the DCF Child Abuse Hotline a dozen times before he was told by the DCF to stop. Teachers and principals from two schools called again and again. They reported that the boy came in with bruises and black eyes, and that he was “always hungry.”

One teacher was so worried that she kept a diary of the boy’s condition. In one entry, she asked one of his brothers why the victim missed two days of school. His answer was alarming: “I don’t even know where he is.”

Teachers’ calls to DCF ended only when the boy was removed to be home-schooled. The agency did nothing to stop that.

“The child does become invisible,” Julia Lynch, who heads child and sex abuse prosecutions in Brevard and Seminole counties, told “America Tonight.” “The child is invisible to anybody, and nobody knows what is going on with that child.”

Over and over, DCF heard about troubles at the home that Glass shared with Michael Marshall, the victim’s father.

Fifteen months later, a chance encounter brought the police to the family’s home in Titusville, Fla., next to Cape Canaveral. The boy was finally rescued.