Bonnie Liltz, 57, who was due to report to prison today for killing her disabled daughter, was found dead in her apartment on Saturday evening, and police suspect she took her own life.

In 2015, Liltz administered a fatal dose of medication to her 28-year-old daughter, Courtney, in their home in Schaumburg, telling the police she feared for her daughter's fate as she faced her own serious health problems.

Schaumburg police said they were called to the apartment just after 6 p.m. by family members who were concerned that they hadn't heard from Liltz since late Friday night. There is no evidence of foul play and suicide is suspected, though an investigation continues, said Schaumburg police Sgt. Christy Lindhurst.

"It's a tragic, tragic end," her attorney, Tom Glasgow, said Sunday. "She just didn't want to die in prison."

Liltz pleaded guilty to involuntary manslaughter in her daughter's death and was sentenced to four years in prison by Cook County Judge Joel Greenblatt, despite prosecutors recommending probation.

When he sentenced her, Greenblatt said she deserved prison time. "The choice you made that morning was not an act of love. It was a crime."

Woman who killed disabled daughter found dead 2 days before returning to prison

She served a few months but, in an unusual move, was granted bond by appellate court judges, allowing her to receive the medical care her lawyer argued she lacked in prison.

But last week she was ordered to report to prison Monday after the Illinois Supreme Court declined to hear the appeal of her sentence.

Her mother, Gladys Liltz, said she was stunned.

"She couldn't do it. She could not go back to that place again," said Gladys Liltz, 89, of Elk Grove Village.

Liltz had adopted Courtney, who couldn't walk or feed herself and needed constant care, and those who knew Liltz during Courtney's upbringing praised her commitment to her daughter. But as her own health worsened - she had lingering and serious side effects from a long-ago bout with cancer - Liltz said she became desperate over concern for her daughter's well-being under someone else's care.

Woman who killed disabled daughter found dead 2 days before returning to prison

Liltz had tried to take her own life after she fed an overdose to her daughter through Courtney's feeding tube. Liltz then flushed down medication with wine.

Glasgow said he talked to Liltz earlier Saturday and there was no indication of any plans to take her life. But he said he had documents from two doctors indicating she would die in prison if she was sent back. He said she left a note.

"It's very upsetting to me because it could have been avoided," Glasgow said.

"She's at peace now, in heaven with her daughter," Gladys Liltz said. "That's all she ever wanted, was to be with Courtney."